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#3383562 - 05/28/14 09:42 PM Pinging goes away after vacuum adv disc - why?
sasilverbullet Offline


Registered: 08/22/04
Posts: 873
Loc: San Antonio, Tx
This one's stumping me - on my newly overhauled 460 in my 70 Lincoln MK III, it pings on acceleration. If I disconnect the vacuum advance it doesn't ping.

Why?

??? ??? ???
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#3383570 - 05/28/14 09:54 PM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
spackard Offline


Registered: 03/24/11
Posts: 727
Loc: CA
Because you're retarding the spark.
Don't you have some delay thingy, maybe hooked onto the air cleaner, that won't give your distributor full vacuum for about 10 seconds?

(Used to own a '73 Marquis with a 429, it had one of the above and I looked it up in a parts manual to see what it did.)
If you don't have a vacuum advance delay then you'll get a lot of pinging every time you accelerate.

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#3383571 - 05/28/14 09:56 PM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
tom slick Offline


Registered: 05/26/03
Posts: 8594
Loc: Central Coast, Calif.
Is the advance hooked to the correct port on the carb?
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#3383575 - 05/28/14 10:07 PM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
crazyoildude Online   content


Registered: 07/23/08
Posts: 5449
Loc: new jersey
Is your timing set to the correct specs? Are u using the correct Gas?

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#3383577 - 05/28/14 10:10 PM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
SuperEd73 Offline


Registered: 08/14/07
Posts: 207
Loc: Glen Cove, NY
When you disconnect the vacuum advance you're only using the mechanical advance weights in the distributor that are based on engine rpms. Couple things you'll need to check: 1) Make sure your base timing is correct. Not sure if you rebuilt your engine back to stock or if it was beefed up in some way. But if your base timing is too high, that could be a problem. 2) You'll need to check the timing advance curve of your distributor and make sure it is correct for your engine. I ran into a problem with that when I purchased a rebuilt distributor for my '68 Dodge. It was rebuilt with the wrong weights and/or springs and it was advancing way too quickly which lead to lots of pinging when the vacuum advance was connected. 3) Check and recheck any rubber lines/fittings for any vacuum leaks. 4) I'm not familiar enough with 1970 emissions standards so I'm not sure if they already started using an EGR valve. If it has it, check for proper operation.

And as tom slick said, check that the vacuum advance line is using the correct port on the carb.

Ed B.
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#3383578 - 05/28/14 10:10 PM Re: Pinging goes away after vacuum adv disc - why? [Re: tom slick]
The_Eric Offline


Registered: 03/31/10
Posts: 3361
Loc: Iowa
Originally Posted By: tom slick
Is the advance hooked to the correct port on the carb?


First thing to check. You do not want full manifold vacuum, but ported vacuum. Failing that, I've have to monkey with cherry picking different part number cans to change the point and amount at which they advance OR use an aftermarket adjustable vacuum advance.

It would also be helpful to know your initial and total advance and also what RPM you're all in by.
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#3383580 - 05/28/14 10:13 PM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
440Magnum Offline


Registered: 02/01/09
Posts: 6337
Loc: Texas
Now you're talkin' my era ;-)

Simple checks:

- vacuum line connected to correct port on the carb (ported or manifold, whichever the car calls for- most cars use ported vacuum)

- make sure timing is set correctly, including being sure that the TDC mark on the crank pulley is really at TDC (sometimes old harmonic balancers rotate on their rubber ring and it throws the timing marks way off).

- Make sure you have the right distributor for the car, with the right vacuum advance servo. Also, some servos are adustable with a small allen wrench stuck down the vacuum nipple (sounds crazy, but its true!) If that adjustment lets the servo apply too much advance for low vacuum, then you'll defnitiely get pinging because it should back off the advance when the manifold pressure rises (vacuum decreases as the throttle opens). I start out with the servo set so that it takes lots of vaccum to engage it (spring is tightest- on Mopar distributors that means turning the allen wrench all the way COUNTER-clockwise). Then I twiddle with it until I notice a little pinging, then back off- takes me a few days of driving to get it right.


Give those a check, and let us know.



Edited by 440Magnum (05/28/14 10:14 PM)
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#3383596 - 05/28/14 10:28 PM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
Kruse Offline


Registered: 10/05/05
Posts: 3074
Loc: Kansas
You might also ask your dyno shop about this.
They ran straight premium gas and it ran fine, no pinging. Remember?

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#3383620 - 05/28/14 11:11 PM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
1 FMF Offline


Registered: 08/12/02
Posts: 1514
Loc: CT
my guess would be you have the distributor vacuum advance connected to ported vacuum on the carb, that is generally wrong.
for basic operation you do want manifold vacuum, because under load you have lower manifold vacuum which reduces distributor vacuum advance. under light load [cruise] conditions you have high manifold vacuum and that causes the distributor vacuum advance to advance ignition timing which is what you want under that condition. under light load cruise if your carb is set up properly it will be on the lean side (for fuel economy reasons) and a lean mixture burns slower and requires more ignition advance. rich mixtures burn quicker and require less ignition advance. you can find many articles online about distributor vacuum advance, the 'ported' vacuum port on the carb was for emissions equipment and various other frankenstein systems of that era. you really need to understand the carb and what ports are what on it, but generally 'ported' vacuum refers to tapping off the vacuum in the carb throat which is mostly opposite of manifold vacuum, as more air flows through the carb ported vacuum signal gets stronger and is not directly related to engine load but more so to throttle position and engine rpm. as the engine picks up rpm and especially if it's under load where you have the power valve or fuel enrichment circuit supplying more fuel you certainly don't want to further advance ignition timing over the distributor mechanical advance.


Edited by 1 FMF (05/28/14 11:15 PM)

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#3383625 - 05/28/14 11:15 PM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
tom slick Offline


Registered: 05/26/03
Posts: 8594
Loc: Central Coast, Calif.
In general, the vacuum advance should not be operating during idle or acceleration, only during even light loading such as driving on the highway. With the vacuum advance disconnected the timing should smoothly go from base timing to about 28* BTDC as the rpm rise. With the vacuum advance connected the timing should continue up to 45* to 50*.

These are numbers I'm pulling out of memory and the actual numbers for your engine may be slightly difference. I haven't owned a vehicle with a vacuum advance for 10 years.
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#3383695 - 05/29/14 05:11 AM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
NHGUY Offline


Registered: 10/09/11
Posts: 3373
Loc: USA
Shouldn't that have a dual diaphragm vacuum valve that the vacuum connects to.A device that bolts to the intake that has inputs from both forms of vacuum (ported and full time) and one vacuum form overrides the other.Maybe its shot or hooked up backwards.

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#3383713 - 05/29/14 06:44 AM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
Trav Offline


Registered: 11/20/06
Posts: 9946
Loc: MA, Mittelfranken.de
As others have said in this thread. It sounds like its hooked to full manifold vacuum.
Put a vacuum gauge on the line you should have zero or almost then it should rise gradually with RPM. If you have full vacuum there you are getting max advance at low RPM causing the pinging.
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#3383791 - 05/29/14 09:03 AM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
sasilverbullet Offline


Registered: 08/22/04
Posts: 873
Loc: San Antonio, Tx
Thanks for all the replies - I'll try and sum up all the answers:

1. Dyno shop ran premium gas only
2. Dyno shop did NOT have anything connected to the vacuum advance
3. Dyno shop said there was no pinging
4. Dyno shop has the timing set to 36 degrees max
5. As per the factory manual - vacuum to the distributor is supplied from the "full time" port on the carb. One line goes from the carb to a three tee distribution mounted on the top of the thermostat housing. Another line comes straight from manifold vacuum. The last line goes off the tee to the distributor.
6. That is a rebuilt dist with Pertronix II installed. I was running that distributor before the engine overhaul - and had a bad pinging problem then also.
7. Engine is not stock, it's now dyno'd at 569HP and 630Ftlbs torque.


I will try a couple of things base on ya'lls suggestions:
1. Use my trusty vacuum gauge to see what actually on the dist line.
2. Depending on the results, probably run a line direct from the "timed" port on the carb to the dist and see how that fairs.
3. Depending on how that all works, might try adjusting the vacuum advance if it's adjustable.
4. If all else fails, ditch the vacuum advance entirely.
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#3383832 - 05/29/14 10:04 AM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
440Magnum Offline


Registered: 02/01/09
Posts: 6337
Loc: Texas
Based on your last post, it sounds like the dyno shop tuned the advance using the "total advance at XXXX RPM" method. That method really (in my experience) works great if you don't ever use vacuum advance, but results in way too much advance when you hook up the vacuum advance. I'm not saying its impossible, but those are the results I've consistently gotten. When I'm planning to use the vac. advance at all, I do the old school "set the base timing at idle with vacuum disconnected, and let total advance fall where it may. If I then go back and look at how much total advance results from that method (comparing apples to apples by leaving the vacuum disconnected during the total advance test), I have always found it to be significantly less than when I set the total advance directly.

It may be that switching to ported vacuum solves the problem, too. Hooking direct to manifold vacuum causes the engine to idle with all the vacuum advance dialed in, so when you first hit the throttle, it takes a fraction of a second for the vacuum advance to retard, and you can get a burst of pinging off the line or during sudden throttle application. And then the engine kinda falls on its face when the advance comes off :-/ That's why I've never liked setting an engine up with manifold vacuum to the advance can, and why so few manufacturers ever did so (Ford in the emissions years being one of them). Ported vacuum was almost universal pre-emissions, and in fact *most* cars remained set up from the factory with ported vacuum advance (and even using orifice valves and thermal valves to delay it even further) right through the emissions years.

I live in the Mopar world- your mileage may vary.
_________________________
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#3383833 - 05/29/14 10:05 AM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
punisher Offline


Registered: 09/11/04
Posts: 1932
Loc: snowblind in TX
I did not know they started all of that thermostatically controlled VSV action back then. Those valves controlled ignition timing depending upon engine temp- more advance when cold, then after engine warmed up timing went to "normal" or timed vacuum from carb.

You might double check the vac diagram and see if one vac to that VSV on the thermostat housing isn't supposed to be timed. Warm the VSV delivers timed vac, cold it delivers full time vac.

Just a thought.

Nice ride by the way. Very familiar with San Antonio as I got all of my FoMoCo certs from their training facility down on South Presa St.

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#3383852 - 05/29/14 10:36 AM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
Vikas Offline


Registered: 07/22/05
Posts: 8232
Loc: NorthEast
If the dyno shop tested it under certain conditions, don't you then need to run the vehicle under similar set up?

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#3383898 - 05/29/14 11:44 AM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
threeputtpar Offline


Registered: 08/04/11
Posts: 1571
Loc: Appleton, WI
I'd agree with 440Magnum, that they set it up wrong in your particular instance.

You'll probably need to start off by checking base timing with the vacuum line to the dist disconnected and plugged. I'm guessing that it will be advanced compared to what your FSM states it should be. You may even have to pull the dist and set it to a different tooth to be able to get it to base spec.

Once set, run it like that with vacuum hooked back up and see what shakes out. Fine tune the base timing from there to get the full advance right up until you just start to get the slightest pinging on acceleration, and then back it off 1 degree.

This is how I had to set the timing on a 1974 Pontiac 400 that I installed in a 1979 Grand Prix in place of the 301. I eventually ditched the original 1974 dist and put a GM HEI in its place.


Edited by threeputtpar (05/29/14 11:46 AM)
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#3383902 - 05/29/14 11:50 AM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
Smoky14 Offline


Registered: 04/23/03
Posts: 985
Loc: Nowhere NM
They make an adjustable vacuum advance. An allen head screw sits inside the vac port. You may luck out and have one.

Smoky
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#3383921 - 05/29/14 12:34 PM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
Volvohead Offline


Registered: 05/25/05
Posts: 3550
Loc: SE Pa
Originally Posted By: sasilverbullet
This one's stumping me - on my newly overhauled 460 in my 70 Lincoln MK III, it pings on acceleration. If I disconnect the vacuum advance it doesn't ping.

Why?

??? ??? ???


As I mentioned in your other post, your pinging issue might be in part caused by the mechanical advance springs. They weaken over time, and then run the advance up too quickly with RPMs. The additional vacuum advance is driving the advance above specs. Sometimes the springs flat out break. It's very common with the Autolites of that period after so many years.

You don't want to disable vacuum advance as it is better related to actual engine loads. Some of the vacuum sections also had dual advance-retard features for early emissions control.

But putting tighter/newer springs in the mechanical advance can eliminate the pinging overall. It's under the breaker plate, and takes all of ten minutes. When we tracked them, there were performance calibrated advance springs available. We could very precisely tune the advance on these. But after 45 years, I don't know what calibrations exist for these old buggers.

Between tighter advance springs and water injection, you can often get those engines running ping free with today's fuels. The only other thing I might add is a little MMO to the fuel to compensate for the unleaded that they were not designed for.

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#3383958 - 05/29/14 01:19 PM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
SteveSRT8 Offline


Registered: 10/10/08
Posts: 15128
Loc: Sunny Florida
Where is the distributor machine? Find a speed shop that has one and tailor the timing as you want it.

It's fully adjustable...
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#3384010 - 05/29/14 02:40 PM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
Chris142 Offline


Registered: 06/05/03
Posts: 11454
Loc: apple valley, ca
How much advance is the vacuum advance giving it? Is the carb jetted lean?
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#3384159 - 05/29/14 05:32 PM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
Merkava_4 Offline


Registered: 01/30/07
Posts: 9363
Loc: Clovis, CA
NOW HEAR THIS -- NOW HEAR THIS:

Your 1970 Lincoln being that it's PRE-smog era probably has right around 11:1 compression. What you need for that is stiffer advance springs on your distributor. How do I know this? Because I put stiffer advance springs on my 1970 Cougar and it did the trick. That basically recurves the timing so that the timing doesn't advance too quickly. Those cars back then were supposed to be fed 108 octane gasoline. 93 was considered a low octane back then.

http://image.highperformancepontiac.com/...nce-springs.jpg

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#3384161 - 05/29/14 05:33 PM Re: Pinging goes away after vacuum adv disc - why? [Re: SteveSRT8]
440Magnum Offline


Registered: 02/01/09
Posts: 6337
Loc: Texas
Originally Posted By: SteveSRT8
Where is the distributor machine? Find a speed shop that has one and tailor the timing as you want it.

It's fully adjustable...



Find a speed shop with someone who still knows how to operate the distributor machine.

:-P
_________________________
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#3384219 - 05/29/14 06:44 PM Re: Pinging goes away after vacuum adv disc - why? [Re: 440Magnum]
Volvohead Offline


Registered: 05/25/05
Posts: 3550
Loc: SE Pa
Originally Posted By: 440Magnum
Originally Posted By: SteveSRT8
Where is the distributor machine? Find a speed shop that has one and tailor the timing as you want it.

It's fully adjustable...



Find a speed shop with someone who still knows how to operate the distributor machine.

:-P



No need for any of that. All you need is a timing light, some marker tape, and a portable tach. And new springs.

Unless you need a shaft and gear rebuild, all you do is risk chewing up the oil seal by pulling the distributor.

You can rebuild and recalibrate the top end of these Autolite distributors with it in the engine. Done dozens of them. Piece of cake.

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#3384232 - 05/29/14 06:53 PM Re: Pinging goes away after vacuum adv disc - why? [Re: punisher]
wag123 Offline


Registered: 06/14/11
Posts: 552
Loc: Texas
It sounds to me like the dyno shop got almost everything right... except maybe the vacuum advance diaphragm, and/or perhaps the power valve in the carburetor, neither of which come into play during a full throttle maximum power output pull.
From what I have read, with the HP that your engine is producing, my guess is that you have a pretty healthy cam in the engine and that it doesn't have all of the 1970 pollution control devices on it anymore. For what you are running, 36 degrees of total mechanical advance should be about right.
As far as the vacuum supply to the distributor, they have that right as well. Lacking an air pump, you should be running manifold vacuum to the distributor, not port vacuum. But, that is NOT the way that it came from the factory. Prior to the use of exhaust air pumps (which started appearing in 1967-1968), distributor advance vacuum was always taken from the manifold. After air pumps were used, distributor advance vacuum was almost always taken from the carburetor throttle vacuum port. The difference is that, with the vacuum advance taken from the manifold, you got about 1/2 of the full vacuum advance at idle. With the vacuum advance taken from the carburetor throttle port, you got ZERO vacuum advance at idle. This is strictly an emissions control thing!
With the HP your are running, total combined advance should be about 46 to 48 degrees (with premium fuel), which means that the distributor vacuum advance diaphragm should only be contributing between 10 to 12 degrees. Also, check your engine vacuum at idle, with the cam you have it is likely around 11-12 inches. At steady-state cruising speed the vacuum is likely about 15-16 inches. If this is the case, the vacuum advance needs to be set up such that it drops out completely below 9-10 inches of vacuum, gives you about 5-6 degrees of advance at 11-12 inches (idle vacuum), and a maximum of 10-12 degrees advance at maximum vacuum (15-16 inches). Adjust these numbers to the actual vacuum readings you are getting from your engine.
Next, the carburetor power valve. The power valve richens up the A-F mixture ratio during acceleration. If the power valve is too lean for your engine, you will get pinging during acceleration because the engine is running too lean. For this you also go by vacuum. For this problem you would need to install a power valve that opens sooner, at a higher vacuum. If the power valve is opening at 5 inches of vacuum, you would need to go with something that opens at 9-10 inches of vacuum.
You might be wondering why the dyno shop didn't check/adjust these things. Because their concern is tuning the engine for a maximum power full throttle pull, not tuning for street drivability at partial throttle settings. None of the above factors affect full throttle pull maximum power output.
To do these adjustments you will need 2 tools, an accurate vacuum gauge, and an adjustable timing light.


Edited by wag123 (05/29/14 07:03 PM)

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#3384240 - 05/29/14 06:58 PM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
Errtt Offline


Registered: 11/14/10
Posts: 2143
Loc: California
When I was a kid and didn't have a timing light, I'd set #1 cylinder on compression stroke, then align the damper timing mark to spec. Then, with loose distributor, slide a piece of the clear wrapper from my smokes between the points, with the distributor retarded and a slight pulling on the clear wrapper, slowly advance the distributor and as soon as the clear wrapper starts to slip, lock down the distributor. Thought - with the timing marks aligned, when the points break contact, the coil field collapse inducing the voltage into the secondary coil windings sending the juice down the plug wire to the spark plug, close to where it should fire, without vacuum advance.
Then test run and tweak the distributor as needed until I can get a hold of someone later with a dwell meter and timing light. Oh, and would spruce up the points if needed with matchbook. If the points lasted long and stayed in good condition, I would keep the same capacitor in it and throw the new/unused in the glovebox.
Must have correct vacuum - clean in the springs and weights etc. Pull vacuum on the hose to the vacuum advance and you should see the plate move.


Edited by Errtt (05/29/14 07:00 PM)
Edit Reason: add

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#3384253 - 05/29/14 07:19 PM Re: Pinging goes away after vacuum adv disc - why? [Re: Merkava_4]
dnastrau Offline


Registered: 12/13/06
Posts: 285
Loc: PA
Originally Posted By: Merkava_4
NOW HEAR THIS -- NOW HEAR THIS:

Your 1970 Lincoln being that it's PRE-smog era probably has right around 11:1 compression. What you need for that is stiffer advance springs on your distributor. How do I know this? Because I put stiffer advance springs on my 1970 Cougar and it did the trick. That basically recurves the timing so that the timing doesn't advance too quickly. Those cars back then were supposed to be fed 108 octane gasoline. 93 was considered a low octane back then.

http://image.highperformancepontiac.com/...nce-springs.jpg


In 1970, Ford required a minimum Research octane of 98 (not 108) in its' premium fuel engines, 94 Research octane for regular fuel engines. This information came from a 1970 Ford owner's manual.

However, fuels in the US and Canada were listed with the Research octane number before about 1975 or so (the same method still used in countries other than the US and Canada today) and then switched to the R+M/2 method that we see on US/Canadian pumps today. That number is 4 - 5 numbers lower than the Research number from 1970. Therefore, the current 93 octane (R+M/2 method) premium should get you about 97 - 98 Research octane - close to the minimum octane required in 1970.

Hopefully the ignition timing tips that Merkava listed above and others have mentioned in this thread will solve your problem without having to resort to additional octane boosters or spiking the tank with racing fuel, etc.

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#3384268 - 05/29/14 07:31 PM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
Volvohead Offline


Registered: 05/25/05
Posts: 3550
Loc: SE Pa
This is from '68 for the 429, but the '70 460 was basically the same. This should get you where you need to be.

http://www.oldcarmanualproject.com/manua...lement_0060.htm

http://www.oldcarmanualproject.com/manuals/Ford/1967/TBird%20Shop/Group%209/pages/Ignition_0020.htm

http://www.oldcarmanualproject.com/manua...lement_0149.htm

Nice that this stuff is now on the internet. All my older books are packed away somewhere, along with my older timing guns and dwell gauges.

This is easy peasy work.

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#3384335 - 05/29/14 08:21 PM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
Trav Offline


Registered: 11/20/06
Posts: 9946
Loc: MA, Mittelfranken.de
A lot of the old engines just run without.

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#3384423 - 05/29/14 09:45 PM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
Chris142 Offline


Registered: 06/05/03
Posts: 11454
Loc: apple valley, ca
The rebuilder lowered the compression to around 8.5-1
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#3384767 - 05/30/14 10:07 AM Re: Pinging goes away after vacuum adv disc - why? [Re: wag123]
440Magnum Offline


Registered: 02/01/09
Posts: 6337
Loc: Texas
Originally Posted By: wag123

As far as the vacuum supply to the distributor, they have that right as well. Lacking an air pump, you should be running manifold vacuum to the distributor, not port vacuum. But, that is NOT the way that it came from the factory. Prior to the use of exhaust air pumps (which started appearing in 1967-1968), distributor advance vacuum was always taken from the manifold. After air pumps were used, distributor advance vacuum was almost always taken from the carburetor throttle vacuum port. The difference is that, with the vacuum advance taken from the manifold, you got about 1/2 of the full vacuum advance at idle. With the vacuum advance taken from the carburetor throttle port, you got ZERO vacuum advance at idle. This is strictly an emissions control thing!


That is simply not true, at least not for all manufacturers. Chrysler virtually NEVER used straight manifold vacuum. My old 1949 Plymouth flathead six used PORT vacuum (through a flared-fitting copper line, no less). All my 50s, 60s, and 70s Mopars used ported vacuum. My '68 Ford 302 (no air pump) used ported vacuum. The 74 Mercury I drove in college used ported vacuum (no air pump, but all the other emissions stuff).

As I pointed out in another post, a huge drawback to manifold vacuum as the source for the advance is that manifold vacuum is at its absolute max at idle- you get 100% advance at idle. But the *instant* you touch the accelerator pedal and crack the butterflies open, manifold vacuum falls off, the timing retards, and (depending on the cam and other factors) the engine will feel like its bogging very badly.

Ported vacuum is zero at idle. When you crack the butterflies open, the transfer slots and vacuum port are exposed to the manifold vacuum (which also drops as the butterflies open) and some (but not 100%) advance is applied, making the engine accelerate smoothly. As the engine speed builds to match the butterfly opening, the ported vacuum continues to increase until full vacuum advance is reached. Now if you step on the gas further, the vacuum will drop and timing will retard to prevent pinging, but since this is already happening at an engine speed well above idle, you don't get the "fall on your face" bog that happens with straight manifold vacuum when you're coming off-idle.
_________________________
'66 Dodge Polara & '69 Dodge Coronet R/T both 440/727
'08 Ram 1500 4.7/545RFE
'12 Challenger SRT8 392/6-speed
'99 Cherokee 4.0, '11 Grand Cherokee 3.6

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#3384818 - 05/30/14 11:33 AM Re: Pinging goes away after vacuum adv disc - why? [Re: 440Magnum]
wag123 Offline


Registered: 06/14/11
Posts: 552
Loc: Texas
I beg to differ 440. I have a LOT of experience in this area.
Ported verses manifold vacuum control of the vacuum distributor advance is a much discussed and widely misunderstood topic. From Lars Grimsrud... "Ported vacuum was used as an emissions control method to retard timing at idle (by eliminating vacuum advance) in order to reduce hydrocarbon emissions."
Just because the vacuum advance is plumbed to the carburetor does NOT mean that it is ported (throttle plate controlled) vacuum. In most cases, this is just a convenient place to put a DEDICATED manifold vacuum port (note in a couple of the attached articles that they tell you NOT to run a "T" in another manifold vacuum line to get your vacuum for the distributor).

To back up what I said, here are some articles...
http://www.460ford.com/forum/showthread.php?t=117504
http://w2ner.com/distributors.htm
http://www.camaros.org/pdf/timing101.pdf
http://www.lbfun.com/warehouse/tech_info/timing%20&%20vacuum%20advance/vacuum_explained.pdf
http://www.lbfun.com/warehouse/tech_info/timing%20&%20vacuum%20advance/Vaacuum_Advance_Specs.pdf

There is a wealth of additional information on the internet about this topic.
I can attest to what they talk about in these articles from personal experience over the last 45 years. There is one thing mentioned in one of the articles that I disagree on, I have found that you should NOT have full vacuum advance at idle. This can cause problems like the OP is experiencing. Most vacuum diaphragms have enough of a response delay in them that they won't cause a idle fluctuation at small idle vacuum variations.
I can also tell everyone from personal experience that IMHO, on a carbureted street driven non-emissions-system-equipped high performance vehicle, you should ALL be using a vacuum advance distributor and you should ALL be using manifold vacuum to control it.


Edited by wag123 (05/30/14 11:46 AM)

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#3384840 - 05/30/14 12:02 PM Re: Pinging goes away after vacuum adv disc - why? [Re: wag123]
Volvohead Offline


Registered: 05/25/05
Posts: 3550
Loc: SE Pa
440 is correct here, at least as it applied to the 385 FoMoCo big block family of the 68-72 era.

As diagrammed in the first vacuum schematic in my earlier post, the early versions of this engine used a two-port temperature regulated valve to supply distributor advance. In normal position, the valve supplied port vacuum. When the engine temperature elevated above threshold, the valve switched to manifold vacuum, which elevated idle speed to aid cooling.

And that is exactly how the system was laid out on every 429 & 460 I dealt with during that period. Simple, and rarely failed.

It's port vacuum advance in normal operation. And it's not that complicated a subject on this particular engine family.

And it's not the cause of the OP's timing problem. Even if the installer hooked up the vacuum advance to manifold, you would know it as soon as you attempted to set initial timing.

If the initial timing is set correctly, this is a mechanical advance problem, and I am very confident of that.

The only other possible cause for erratic timing is an aftermarket electronic breaker unit that has gone haywire. When these electronic things first came out, I still preferred a good set of blue streaks, which were more accurate and dependable.

. . . I wouldn't have castrated this engine down to 8.5/1 to begin with, but that's another issue. They run fine at 10.5/1 stock on today's fuels.

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#3384848 - 05/30/14 12:08 PM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
Oldswagon Offline


Registered: 01/23/03
Posts: 765
Loc: ON
Most Ford's reduced ignition timing at idle by way of a dual diaphragm vacuum advance unit. The front part was connected to ported vacuum like most other vacuum advances. It has a rear diaphragm that connected to manifold vacuum. This system reduce the ignition advance at idle and when decelerating and caused less hydrocarbon emissions. Many 1970 Ford V8's, including high performance engines, used these dual diaphragm advance units.

To OP, if you are still using a Ford distributor (or rebuilt Ford) and not a high performance aftermarket unit, you can adjust the vacuum advance canister with a 1/8" Allen wrench in the vacuum port. As others have said you need to check the specs and adjust your mechanical advance and vacuum advance. Bringing them back to stock specs should get rid of the ping.

Here are the stock specs for a 1970 460 distributor (note RPM is distributor RPM, thus 1/2 engine RPM).

Mechanical Advance:

0@500 RPM
11@2575

Vacuum Advance:

0-1 @ 5 Ins HG
12 @ 25 Ins HG

Dwell Angle:
26-31

Static Timing:

6 BTDC

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#3384857 - 05/30/14 12:18 PM Re: Pinging goes away after vacuum adv disc - why? [Re: 440Magnum]
SteveSRT8 Offline


Registered: 10/10/08
Posts: 15128
Loc: Sunny Florida
Originally Posted By: 440Magnum
Originally Posted By: SteveSRT8
Where is the distributor machine? Find a speed shop that has one and tailor the timing as you want it.

It's fully adjustable...



Find a speed shop with someone who still knows how to operate the distributor machine.

:-P


Got one right here in the backwoods of Florida! It's hardly rocket science, as Volvohead says you can also do this in the driveway with hand tools.

I always used to set my distributor vehicles by ear anyway, only use a machine on specific cam and head combos that had some specs supplied. And of course you remember my remark a LONG time ago how we called it "vacuum retard" not advance? Just depends on the setup.

Without knowing the cam specs that compression seems kind of low, but maybe we're going for regular fuel?
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#3384891 - 05/30/14 12:55 PM Re: Pinging goes away after vacuum adv disc - why? [Re: Oldswagon]
Volvohead Offline


Registered: 05/25/05
Posts: 3550
Loc: SE Pa
Originally Posted By: Oldswagon
Most Ford's reduced ignition timing at idle by way of a dual diaphragm vacuum advance unit.


NOT in 1970, NOT in a standard "cobrajet" 429/460 build on an AUTOMATIC.

At that time, this engine series was the latest "IMCO" design, didn't need air pumps, a two port diaphragm, or any other emissions control, until at least '71 (I think it was even later, but it's been a lot of years).

The dual diaphragm distributor was also typically used on manual transmission vehicles early on, and on other engine families:

http://www.428cobrajet.org/id-dist-vac-advance

Sometime after '71, Ford dropped the compression on the 460s down near 8:1. There is a huge difference between a 385 series engine from '68-'71/72 and the later ones.

By the mid '70s they were ALL loaded down with emissions junk (including dual diaphragm advance), castrated down to lower compression, and running on unleaded swill.

But the early ones (like this one) were real beasties, with compression as high as 11:1. And they all had single diaphragm advance. And with the C6, the fuel and ignition systems were very simple and dependable.

The SCJ (Super cobrajet) and Boss versions were altogether another build, with the Boss having PITA head gaskets and being completely unmanageable on the street.

This distributor fitted about 8 different engines, not just the 385 series. So you will see rebuilders fitting them with replacement distributors and advance units showing two vacuum ports. But that's WRONG, and not what the early ones came with.

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#3384892 - 05/30/14 12:57 PM Re: Pinging goes away after vacuum adv disc - why? [Re: SteveSRT8]
wag123 Offline


Registered: 06/14/11
Posts: 552
Loc: Texas
Guys, the OP obviously does not have a stock engine. The hardware, vacuum connections, and timing settings you are referring too are for a stock-from-the-factory early emissions controlled engine. All of my advice was on to how the OP could get the best street driveability and fuel mileage out of his less-than-stock setup based on my past experiences doing this sort of thing (he is already getting his full measure of WOT performance from having it dyno-tuned).
BTW, the advice I gave about timing settings assume that the distributor's centrifugal advance is working properly and it's advance curve set-up properly. The dyno tuner should have done this for him.
You don't need to take the distributor to a shop to get it setup. For as little as $50-$70 one can obtain an adjustable advance timing light, and for under $20 one can obtain a fairly accurate vacuum gauge. Using these simple tools one can see EXACTLY what is going on with this engine and make the necessary modifications/adjustments as needed, IN THE DRIVEWAY. Distributor advance springs, weights, and other parts are quite inexpensive (if needed). If the OP doesn't already have an adjustable vacuum diaphragm, these can be purchased for $30 to $50.


Edited by wag123 (05/30/14 12:59 PM)

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#3384915 - 05/30/14 01:38 PM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
Volvohead Offline


Registered: 05/25/05
Posts: 3550
Loc: SE Pa
Yes, it would be helpful if the OP explained exactly what he had at this point.

But unless this has been fitted with an aftermarket distributor, I think it's most likely a mechanical advance fault. The vacuum motors typically malfunction open. The only other possibility is if someone removed the vacuum calibration spring.

But until he clarifies, it is all so much speculation.

I still don't get castrating down a pre-smog engine like this. They run fine on 93 with simple steps.

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#3384930 - 05/30/14 02:02 PM Re: Pinging goes away after vacuum adv disc - why? [Re: Volvohead]
Oldswagon Offline


Registered: 01/23/03
Posts: 765
Loc: ON
Originally Posted By: Volvohead


NOT in 1970, NOT in a standard "cobrajet" 429/460 build on an AUTOMATIC.

A


Who's talking about 1970 429CJs?? And that link was for the 428 CJ engines. This is a 1970 460-4V from a Mark III, a car that ran 17 sec 1/4 mile times. That said, I pulled my 1970 Motor Trend where they test a 1970 Torino 429CJ vs a Chevelle LS6 454 and a 440 Road Runner. There is a clear under the hood shot on the Torino showing a dual diaphragm vacuum advance canister.

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#3384935 - 05/30/14 02:12 PM Re: Pinging goes away after vacuum adv disc - why? [Re: wag123]
440Magnum Offline


Registered: 02/01/09
Posts: 6337
Loc: Texas
Originally Posted By: wag123
I beg to differ 440. I have a LOT of experience in this area.
Ported verses manifold vacuum control of the vacuum distributor advance is a much discussed and widely misunderstood topic. From Lars Grimsrud... "Ported vacuum was used as an emissions control method to retard timing at idle (by eliminating vacuum advance) in order to reduce hydrocarbon emissions."
Just because the vacuum advance is plumbed to the carburetor does NOT mean that it is ported (throttle plate controlled) vacuum. In most cases, this is just a convenient place to put a DEDICATED manifold vacuum port (note in a couple of the attached articles that they tell you NOT to run a "T" in another manifold vacuum line to get your vacuum for the distributor).

To back up what I said, here are some articles...
http://www.460ford.com/forum/showthread.php?t=117504
http://w2ner.com/distributors.htm
http://www.camaros.org/pdf/timing101.pdf
http://www.lbfun.com/warehouse/tech_info/timing%20&%20vacuum%20advance/vacuum_explained.pdf
http://www.lbfun.com/warehouse/tech_info/timing%20&%20vacuum%20advance/Vaacuum_Advance_Specs.pdf

There is a wealth of additional information on the internet about this topic.
I can attest to what they talk about in these articles from personal experience over the last 45 years. There is one thing mentioned in one of the articles that I disagree on, I have found that you should NOT have full vacuum advance at idle. This can cause problems like the OP is experiencing. Most vacuum diaphragms have enough of a response delay in them that they won't cause a idle fluctuation at small idle vacuum variations.
I can also tell everyone from personal experience that IMHO, on a carbureted street driven non-emissions-system-equipped high performance vehicle, you should ALL be using a vacuum advance distributor and you should ALL be using manifold vacuum to control it.


Don't know what to say, other than "my ~35 years of experience is in direct opposition to yours." Mopar NEVER used manifold vacuum. I have less experience with Ford, what I do have is similar. I indeed know that most carbs have a ported vacuum and a manifold vacuum fitting... but at least 80% of the stock setups I've personally dealt with used the ported vacuum nipple. I know for a fact that all the following used ported vacuum from the factory: '49 Plymouth flathead, '66 Plymouth 361, '66 Dodge 383, '65 Chrysler 300L, '69 Coronet R/T 440, '69 Ford Ranchero 302, '73 Satellite 318 (with OSAC- Orifice Spark Advance Control- added for emissions), 74 Mercury Comet 250 1V, 74 Dart 318 (with OSAC added for emissions).

OSAC was a driveability and fuel economy nightmare intended to reduce NOx. It took ported vacuum as the input, and once the engine was at operating temperature it routed the vacuum signal through a check valve with a TINY pinhole so that it took many seconds for the distributor advance chamber to pump down, but the vacuum would all be dumped very quickly when the vacuum signal went away. So a short stoplight-to-stoplight run would never let the vacuum advance engage at all. It pretty much took vacuum advance out of the picture for city driving, and you only got full advance during steady cruising on the highway. And one blip of the throttle would dump all the built-up vacuum and you started over again. Not to mention the fact that the orifice would clog easily, which just killed the vacuum advance ALL the time.

Incidentally, there's one other thing that's dead wrong in the article you quoted. It says that using ported vacuum is an emission control device used to lower hydrocarbon emission. Using ported vacuum at idle lowers NOx, and actually RAISES hydrocarbon emissions. Running a ton of advance at low RPM creates higher peak combustion temps, which directly contribute to NOx emissions. Simlarly, a later spark can result in less complete combustion, raising unburned HCs. So its really not an emissions winner either way.


Edited by 440Magnum (05/30/14 02:24 PM)
_________________________
'66 Dodge Polara & '69 Dodge Coronet R/T both 440/727
'08 Ram 1500 4.7/545RFE
'12 Challenger SRT8 392/6-speed
'99 Cherokee 4.0, '11 Grand Cherokee 3.6

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#3385012 - 05/30/14 03:55 PM Re: Pinging goes away after vacuum adv disc - why? [Re: 440Magnum]
wag123 Offline


Registered: 06/14/11
Posts: 552
Loc: Texas
Originally Posted By: 440Magnum
Incidentally, there's one other thing that's dead wrong in the article you quoted. It says that using ported vacuum is an emission control device used to lower hydrocarbon emission. Using ported vacuum at idle lowers NOx, and actually RAISES hydrocarbon emissions.

You are absolutely right! I didn't catch that one.
Now, the OP's car COULD have the centrifugal advance curve set up in such a way that it is advancing WAY too early in the RPM range (like just off of idle). Adding-in vacuum advance can push it over the top and cause the pinging. On engines that I set up for the street, I like to have the centrifugal advance start to move at 1500 to 1600 RPMs and be all-in by about 2700 to 2800 RPMs. But, with only a 8.5:1 compression ratio, he should be able to run a TON of advance and still not have it ping. Using 93 octane fuel, at that compression ratio he should be able to run as high as 52 degrees of total advance at as low as 2500 RPMs without a pinging problem. That is why I mentioned the carburetor power valve. It could be either... way too lean or not functioning at all.
All of the possibilities we are throwing out are just guesses. First off, we don't know what he is running for a cam or carburetion. And, until the OP puts a timing light and vacuum gauge on it, ALL we can do is guess about what the possible problem might be.


Edited by wag123 (05/30/14 04:05 PM)

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#3385045 - 05/30/14 04:39 PM Re: Pinging goes away after vacuum adv disc - why? [Re: wag123]
440Magnum Offline


Registered: 02/01/09
Posts: 6337
Loc: Texas
Originally Posted By: wag123
Originally Posted By: 440Magnum
Incidentally, there's one other thing that's dead wrong in the article you quoted. It says that using ported vacuum is an emission control device used to lower hydrocarbon emission. Using ported vacuum at idle lowers NOx, and actually RAISES hydrocarbon emissions.

You are absolutely right! I didn't catch that one.
Now, the OP's car COULD have the centrifugal advance curve set up in such a way that it is advancing WAY too early in the RPM range (like just off of idle). Adding-in vacuum advance can push it over the top and cause the pinging. On engines that I set up for the street, I like to have the centrifugal advance start to move at 1500 to 1600 RPMs and be all-in by about 2700 to 2800 RPMs.


I think you're right.

From what he said about the dyno shop, I really think they did a pretty good job... of setting it up to run its best WITHOUT a vacuum advance. I've seen a lot of strip cars set up that way, and you can't just hook the advance back up and go drive it on the street (usually) once that's done. Gotta set up both together if you're ever going to use vacuum. The old Mopar big-block wedge head rule-of-thumb for no vacuum advance and dragstrip use was "38 degrees total advance, ALL IN BY 1200 RPM (then adjust from there for your specific cam)." HAving all the mechanical advance in that fast just will not work with vacuum advance in the mix.

Total advance is VERY dependent on combustion chamber shape, too. The Hemis and wedge big-blocks liked different amounts of total advance, even with the same rotating assembly and similar cam profiles.
_________________________
'66 Dodge Polara & '69 Dodge Coronet R/T both 440/727
'08 Ram 1500 4.7/545RFE
'12 Challenger SRT8 392/6-speed
'99 Cherokee 4.0, '11 Grand Cherokee 3.6

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#3385054 - 05/30/14 04:49 PM Re: Pinging goes away after vacuum adv disc - why? [Re: Oldswagon]
Oldswagon Offline


Registered: 01/23/03
Posts: 765
Loc: ON
Originally Posted By: Oldswagon
Originally Posted By: Volvohead


NOT in 1970, NOT in a standard "cobrajet" 429/460 build on an AUTOMATIC.

A


Who's talking about 1970 429CJs?? And that link was for the 428 CJ engines. This is a 1970 460-4V from a Mark III, a car that ran 17 sec 1/4 mile times. That said, I pulled my 1970 Motor Trend where they test a 1970 Torino 429CJ vs a Chevelle LS6 454 and a 440 Road Runner. There is a clear under the hood shot on the Torino showing a dual diaphragm vacuum advance canister.



I forgot to mention that the 429 Torino was an automatic.

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#3385060 - 05/30/14 05:06 PM Re: Pinging goes away after vacuum adv disc - why? [Re: 440Magnum]
wag123 Offline


Registered: 06/14/11
Posts: 552
Loc: Texas
Originally Posted By: 440Magnum

The old Mopar big-block wedge head rule-of-thumb for no vacuum advance and dragstrip use was "38 degrees total advance, ALL IN BY 1200 RPM (then adjust from there for your specific cam)." HAving all the mechanical advance in that fast just will not work with vacuum advance in the mix.

Now THAT explains a LOT!!!
If this is indeed the case, the OP will need to start from scratch with his distributor setup and timing settings. The good thing is that, done right, he won't loose any of the power that the engine makes at WOT.

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#3385078 - 05/30/14 05:44 PM Re: Pinging goes away after vacuum adv disc - why? [Re: wag123]
wag123 Offline


Registered: 06/14/11
Posts: 552
Loc: Texas
Thanks for jogging my aging and increasingly feeble memory 440! I had forgotten all about that.
Back in the day (many, MANY moons ago) when I was into drag racing, that is EXACTLY how we setup the timing on our drag race engines. It is how we made the cars come out of the hole like BIG DOGS! But, this was on DEDICATED drag cars, not street cars that served as daily use transportation and occasionally drag raced on a Friday night now and then.
Putting an adjustable timing light on the car will tell the truth IMMEDIATELY!


Edited by wag123 (05/30/14 05:49 PM)

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#3385084 - 05/30/14 05:50 PM Re: Pinging goes away after vacuum adv disc - why? [Re: wag123]
Merkava_4 Offline


Registered: 01/30/07
Posts: 9363
Loc: Clovis, CA
Originally Posted By: wag123
I can also tell everyone from personal experience that IMHO, on a carbureted street driven non-emissions-system-equipped high performance vehicle, you should ALL be using a vacuum advance distributor and you should ALL be using manifold vacuum to control it.


Isn't manifold vacuum full strength vacuum at idle? Back in the day, we'd have the vacuum hose going from the distributor advance diaphragm to the ported vacuum hookup on the carburetor (above the throttle plate) - that way the vacuum would gradually increase as you accelerate off of idle.

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#3385090 - 05/30/14 05:58 PM Re: Pinging goes away after vacuum adv disc - why? [Re: Merkava_4]
wag123 Offline


Registered: 06/14/11
Posts: 552
Loc: Texas
Originally Posted By: Merkava_4
Originally Posted By: wag123
I can also tell everyone from personal experience that IMHO, on a carbureted street driven non-emissions-system-equipped high performance vehicle, you should ALL be using a vacuum advance distributor and you should ALL be using manifold vacuum to control it.


Isn't manifold vacuum full strength vacuum at idle? Back in the day, we'd have the vacuum hose going from the distributor advance diaphragm to the ported vacuum hookup on the carburetor (above the throttle plate) - that way the vacuum would gradually increase as you accelerate off of idle.

No. Vacuum will be at it's maximum when the car is at a low-load steady-state cruising speed.
Go to the links that I left a few posts back and read them.

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#3385324 - 05/30/14 11:08 PM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
artificialist Offline


Registered: 09/23/07
Posts: 6899
Loc: Florida
When your car was built, I don't know if gasoline had ethanol added to it, but now in many cases it does. Do you know if the fuel used by the rebuilder had ethanol? When ethanol is added, it leans the AFR in engines that don't have O2 sensors. Leaning the AFR can result in knock if ignition timing isn't changed to compensate.

And of course, one of the problems you may be encountering is how the smog devices were configured on the dyno, versus in your car.

Do you have any vacuum leaks? I remember working with a 70s Lincoln, and I noticed many vacuum operated devices. If any of those leaked, you could have an incorrect AFR, and those devices wouldn't be attached to the engine while dyno testing.
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#3386884 - 06/02/14 10:39 AM Re: Pinging goes away after vacuum adv disc - why? [Re: Merkava_4]
440Magnum Offline


Registered: 02/01/09
Posts: 6337
Loc: Texas
Originally Posted By: Merkava_4


Isn't manifold vacuum full strength vacuum at idle? Back in the day, we'd have the vacuum hose going from the distributor advance diaphragm to the ported vacuum hookup on the carburetor (above the throttle plate) - that way the vacuum would gradually increase as you accelerate off of idle.


Yes, except for "big" cams (with a lot of overlap). Almost every stock factory cam from the 60s-80s will produce max vacuum at idle, buta lot of aftermarket cams won't pull enough vacuum at idle to run power brakes. They have to be spinning ~2000 RPM under light load to hit maximum vacuum. Also when these "big" cams are idling, the vacuum becomes very erratic. The idle speed lopes and surges under the best of conditions and connecting to manifold vacuum can make that even worse, since now you have the advance surging around and feeding back making the engine surge worse.
_________________________
'66 Dodge Polara & '69 Dodge Coronet R/T both 440/727
'08 Ram 1500 4.7/545RFE
'12 Challenger SRT8 392/6-speed
'99 Cherokee 4.0, '11 Grand Cherokee 3.6

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#3387124 - 06/02/14 03:50 PM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
sasilverbullet Offline


Registered: 08/22/04
Posts: 873
Loc: San Antonio, Tx
Originally Posted By: sasilverbullet
...I will try a couple of things base on ya'lls suggestions:
1. Use my trusty vacuum gauge to see what actually on the dist line.
2. Depending on the results, probably run a line direct from the "timed" port on the carb to the dist and see how that fairs.
3. Depending on how that all works, might try adjusting the vacuum advance if it's adjustable.
4. If all else fails, ditch the vacuum advance entirely.


OP update - I tried pretty much everything everyone suggested except changing the mechanical springs out and the only thing that works is running with the vacuum advance disconnected.

What I don't understand is why the "timed" port on my Edelbrock 1406 doesn't look any different on the vacuum gauge compared to the other port on the carb and straight from the manifold??

So I'm just running the mechanical advance - it doesn't ping and seems to be running fine.

I'll leave it like this for a while and see how things go.
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#3387146 - 06/02/14 04:33 PM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
wag123 Offline


Registered: 06/14/11
Posts: 552
Loc: Texas
Originally Posted By: sasilverbullet
Originally Posted By: sasilverbullet
...I will try a couple of things base on ya'lls suggestions:
1. Use my trusty vacuum gauge to see what actually on the dist line.
2. Depending on the results, probably run a line direct from the "timed" port on the carb to the dist and see how that fairs.
3. Depending on how that all works, might try adjusting the vacuum advance if it's adjustable.
4. If all else fails, ditch the vacuum advance entirely.


OP update - I tried pretty much everything everyone suggested except changing the mechanical springs out and the only thing that works is running with the vacuum advance disconnected.

What I don't understand is why the "timed" port on my Edelbrock 1406 doesn't look any different on the vacuum gauge compared to the other port on the carb and straight from the manifold??

So I'm just running the mechanical advance - it doesn't ping and seems to be running fine.

I'll leave it like this for a while and see how things go.

I suspect that the idle throttle opening may be too far open to close off the port vacuum holes in the carburetor throat.

BTW: Going back to what I said about using manifold vs port vacuum for the vacuum advance, I found this statement in the Edelbrock 1406 owners manual...
Long Duration Camshaft
If the engine has a fairly radical camshaft it may require an excessive amount of throttle
opening for idle and/or have low idle vacuum levels. Either condition can lead to poor levels of adjustability and erratic idles.
Another fix for the above condition is to run as much spark advance as possible at idle. If the distributor is fitted with a vacuum advance unit, connect it directly to manifold vacuum. If you are not able to employ vacuum advance for some reason, then the mechanical curve should have a low limit, which will allow you to use plenty of initial spark advance.

The last sentence sounds like what the dyno tuner did. You will never know unless you check it with a timing light.
If the car runs good with the vacuum advance disconnected, then run it that way and don't worry about it. But, if you could get the vacuum advance working so you could add another 12 to 15 degrees of advance at low load light throttle settings, you could experience a fairly significant gain in cruising fuel mileage.

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#3387807 - 06/03/14 11:40 AM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
440Magnum Offline


Registered: 02/01/09
Posts: 6337
Loc: Texas
Originally Posted By: sasilverbullet

What I don't understand is why the "timed" port on my Edelbrock 1406 doesn't look any different on the vacuum gauge compared to the other port on the carb and straight from the manifold??

So I'm just running the mechanical advance - it doesn't ping and seems to be running fine.

I'll leave it like this for a while and see how things go.


This is a Lima Ford engine right? Takes a lot of air to idle one of those ;-) I imagine that the Edelbrock doesn't have enough air flow to idle the engine without the throttle blades being cracked open far enough to expose the transfer slots and ports to manifold vacuum. Common problem on big-displacement engines, actually, my 440s are the same way. The ideal solution is to set the idle speed where you want it, remove the carb, flip it over, and see where the throttle blades are with the throttle against the idle stop. If they're exposing the ports and slots, drill a small air bleed hole in each throttle blade near the idle fuel inlet side of the blade. That lets you close the blades and cover the ports while still maintaining enough air flow for idle. Factory big-block carbs usually already have holes in the throttle blades.

But obviously doing this is not easily reversible- proceed with caution and start small!
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#3387906 - 06/03/14 02:18 PM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
Gokhan Offline


Registered: 12/29/10
Posts: 1558
Loc: Los Angeles, California
Originally Posted By: sasilverbullet
This one's stumping me - on my newly overhauled 460 in my 70 Lincoln MK III, it pings on acceleration. If I disconnect the vacuum advance it doesn't ping.

Why?

??? ??? ???

Of course, engines ping when you advance the ignition timing too much.

The optimal timing is such that the engine pings very lightly when the transmission gently shifts to overdrive on a slight upward slope. If that's the case, you have the optimal compromise between fuel economy + horse power (more advanced ignition timing the better for that purpose) and engine pinging + emissions (more retarded timing the better for that purpose). Therefore, do the test I explained and adjust the ignition timing for light pinging under those conditions.
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#3388702 - 06/04/14 01:21 PM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
SteveSRT8 Offline


Registered: 10/10/08
Posts: 15128
Loc: Sunny Florida
Originally Posted By: sasilverbullet

OP update - I tried pretty much everything everyone suggested except changing the mechanical springs out and the only thing that works is running with the vacuum advance disconnected.

What I don't understand is why the "timed" port on my Edelbrock 1406 doesn't look any different on the vacuum gauge compared to the other port on the carb and straight from the manifold??

So I'm just running the mechanical advance - it doesn't ping and seems to be running fine.

I'll leave it like this for a while and see how things go.


As stated by many here the advance can be set by simply adjusting to the pinging threshold. No ping at all means you need more advance!


Use the gas you want and the engine needs to be HOT. With the timing advanced the engine will be much more responsive and fun, retarded timing really takes your throttle response with it...


Edited by SteveSRT8 (06/04/14 01:21 PM)
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#3389004 - 06/04/14 06:55 PM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
flanso Offline


Registered: 12/26/06
Posts: 323
Loc: Houston, TX
Originally Posted By: sasilverbullet
[quote=sasilverbullet]
What I don't understand is why the "timed" port on my Edelbrock 1406 doesn't look any different on the vacuum gauge compared to the other port on the carb and straight from the manifold??


The spark port in an emission controlled carburetor is slightly further above the the fully closed throttle valve than in a non-emission carb. The higher spark port delays the vacuum signal to the distributor. That delay reduces hydrocarbons but may compromise drivability. If you're happy with drivability, go with the vacuum advance disconnected. If you would like the vacuum connected, retard your initial timing until it barely pings. Then adjust the stop for the mechanical advance, under the breaker plate, so you get the same total advance as you did before before you retarded the timing.

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#3389106 - 06/04/14 08:47 PM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
1 FMF Offline


Registered: 08/12/02
Posts: 1514
Loc: CT
Originally Posted By: sasilverbullet
[quote=sasilverbullet]

What I don't understand is why the "timed" port on my Edelbrock 1406 doesn't look any different on the vacuum gauge compared to the other port on the carb and straight from the manifold??


because it's a 460 and you have a 600 cfm carb if i read the correct posts by you in a previous thread. you most likely have the throttle blades open too far to allow enough air in for idle and you've exposed the ported vacuum port. so at idle for you your delayed ported vacuum source is basically the same as full manifold vacuum. if you pull the carb and look at where you have the throttle blades set for idle via the idle stop screw, i'll bet the ported vacuum hole is exposed below the throttle blade.

also, what i wrote previously when i said ported I meant venturi vacuum.

here is [another] good read on the subject:
http://www.corvetteactioncenter.com/foru...um-advance.html

did you ever mention what you had done to the motor, what heads you are running and what camshaft ? I only found edelbrock 2166 dual plane intake and 1406 carb.
are you running the oem distributor and coil, what are you running for an ignition?
and what intake manifold vacuum reading are you getting at 800 rpm and 2000 rpm in neutral?
i don't know what's available these days for distributor based ignitions, but if it were me i would be looking for a programmable box that runs with a MAP sensor and lets you program a spark advance table to your hearts content with a laptop. MSD ought to have something like that at least. It all comes down to what your ignition timing is based on rpm and engine load where engine load is based on intake manifold vacuum. google spark advance maps or ignition timing maps if you are not familiar, that's what you are creating with your mechanical advance springs and vacuum advance can in the distributor. if you know your distributor mechanical advance curve and how the vacuum advance works, then engine rpm and an intake manifold vacuum gauge will give you the data so you can populate your [analog] spark table and see what's going on with what you have now.

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#3389682 - 06/05/14 11:46 AM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
sasilverbullet Offline


Registered: 08/22/04
Posts: 873
Loc: San Antonio, Tx
I just ordered a adjustable vacuum advance and some springs for the mechanical advance. Stay tuned...
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#3389751 - 06/05/14 12:50 PM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
Gokhan Offline


Registered: 12/29/10
Posts: 1558
Loc: Los Angeles, California
Originally Posted By: sasilverbullet
I just ordered a adjustable vacuum advance and some springs for the mechanical advance. Stay tuned...

Springs for the mechanical advance don't go bad. However, what goes bad is the governor shaft, which tends to weld onto the distributor shaft because the grease used is usually of poor quality and dries over time. If that's the case, the only workaround is to replace the distributor altogether, as you can't replace the shaft.

I recently rebuilt my distributor and generously lubricated the mechanical-advance shaft with Valvoline 100%-synthetic grease with moly. The OEM distributor wasn't even that old (about nine years) but there was already some lubrication loss in the shaft and there were some small wear scars.

If your mechanical advance is shot due to lubrication loss and heavy wear, I guess you could try to make up for it by tuning your adjustable vacuum advance. The distributors are really expensive and you may not even be able to find one.

I wonder why they wouldn't make some electronic aftermarket distributors. They would be far more reliable and cheaper than the early-20th-century mechanical-distributor technology.
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#3389821 - 06/05/14 02:22 PM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
wag123 Offline


Registered: 06/14/11
Posts: 552
Loc: Texas
Originally Posted By: sasilverbullet
I just ordered a adjustable vacuum advance and some springs for the mechanical advance. Stay tuned...

Now, you need to bum an adjustable advance timing light from someone. If you don't know anybody that has one, buy one for $55 or so off Amazon. You don't need to buy an expensive one because you won't be getting very much use out of it. Make sure you buy one with the adjustable advance, don't cheap out! You don't need one with a digital adjuster, the dial type is fine, that is what I have and I actually prefer the dial.
http://www.amazon.com/Actron-CP7528-Advance-Timing-Light/dp/B000BSWEHS/


Edited by wag123 (06/05/14 02:24 PM)

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#3389904 - 06/05/14 03:54 PM Re: Pinging goes away after vacuum adv disc - why? [Re: wag123]
Gokhan Offline


Registered: 12/29/10
Posts: 1558
Loc: Los Angeles, California
Originally Posted By: wag123
Originally Posted By: sasilverbullet
I just ordered a adjustable vacuum advance and some springs for the mechanical advance. Stay tuned...

Now, you need to bum an adjustable advance timing light from someone. If you don't know anybody that has one, buy one for $55 or so off Amazon. You don't need to buy an expensive one because you won't be getting very much use out of it. Make sure you buy one with the adjustable advance, don't cheap out! You don't need one with a digital adjuster, the dial type is fine, that is what I have and I actually prefer the dial.
http://www.amazon.com/Actron-CP7528-Advance-Timing-Light/dp/B000BSWEHS/

I wouldn't go analog, as the digital ones come with a tachometer and are far easier to use and more accurate.

I have had an Innova for many years and the light bulb still hasn't burned out. I had bought a cheap $30 one (likely the Actron brand) and the bulb burned out after a few minutes of use. I would definitely recommend the Innova. The one I have is the following one and it's only $80. I had paid about $100 about 15 years ago:

http://www.amazon.com/INNOVA-3568-Digital-Timing-Light/dp/B000EVYGV4/
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1985 Toyota Corolla LE, 4A-LC engine, ~ 257,000 M
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#3390524 - 06/06/14 09:54 AM Re: Pinging goes away after vacuum adv disc - why? [Re: wag123]
threeputtpar Offline


Registered: 08/04/11
Posts: 1571
Loc: Appleton, WI
Originally Posted By: wag123
Originally Posted By: sasilverbullet
I just ordered a adjustable vacuum advance and some springs for the mechanical advance. Stay tuned...

Now, you need to bum an adjustable advance timing light from someone. If you don't know anybody that has one, buy one for $55 or so off Amazon. You don't need to buy an expensive one because you won't be getting very much use out of it. Make sure you buy one with the adjustable advance, don't cheap out! You don't need one with a digital adjuster, the dial type is fine, that is what I have and I actually prefer the dial.
http://www.amazon.com/Actron-CP7528-Advance-Timing-Light/dp/B000BSWEHS/


wag123, the OP is also in TX. You should see if you're close and offer to lend a tool or a hand.
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#3390755 - 06/06/14 02:33 PM Re: Pinging goes away after vacuum adv disc - why? [Re: threeputtpar]
sasilverbullet Offline


Registered: 08/22/04
Posts: 873
Loc: San Antonio, Tx
Originally Posted By: threeputtpar
...wag123, the OP is also in TX. You should see if you're close and offer to lend a tool or a hand.


LOL Texas is a BIG state! But I'm just north of San Antonio in Bulverde.
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#3391005 - 06/06/14 07:42 PM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
Gokhan Offline


Registered: 12/29/10
Posts: 1558
Loc: Los Angeles, California
A tachometer / timing light is a must-have for all DIYers with adjustable idle speed and ignition timing. I would definitely have my own.
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#3391068 - 06/06/14 08:55 PM Re: Pinging goes away after vacuum adv disc - why? [Re: Gokhan]
artificialist Offline


Registered: 09/23/07
Posts: 6899
Loc: Florida
Originally Posted By: Gokhan

I wonder why they wouldn't make some electronic aftermarket distributors. They would be far more reliable and cheaper than the early-20th-century mechanical-distributor technology.

MSD makes a computerized distributor for such old cars. There were some screws you would turn that would change advance by RPM, and vacuum advance had similar adjustments. Instead of a vacuum actuator, the special distributor used a MAP sensor.

I looked online for one that fits a Ford 460, but I didn't see one. I have seen them on more common V8 engines like the Chevy 350 and Ford 302.
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#3392413 - 06/08/14 06:36 PM Re: Pinging goes away after vacuum adv disc - why? [Re: sasilverbullet]
sasilverbullet Offline


Registered: 08/22/04
Posts: 873
Loc: San Antonio, Tx
WooHoo!!! Cheers2

Thanks everyone for helping me conquer this problem! I ordered a Crane Cams adjustable vacuum advance, followed what you guys said, and the directions in the box.

With no vacuum advance I had to adjust the initial timing from 10 to 8 to get all the pinging out.

Then I connected up the vacuum advance and adjusted it until the pinging went away.

Fyi, I had to do a LOT of bending to the arm on the vacuum advance.

Thanks again everyone! USA


Edited by sasilverbullet (06/08/14 06:36 PM)
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