Pinging goes away after vacuum adv disc - why?

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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
 
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
 
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.
 
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.
 
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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.
 
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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.
 
A lot of the old engines just run without.

1969SuperBoss429-2.jpg
 
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.
 
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 & vacuum advance/vacuum_explained.pdf
http://www.lbfun.com/warehouse/tech_info/timing & vacuum advance/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.
 
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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.
 
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
 
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?
 
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.
 
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.
 
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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.
 
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.
 
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 & vacuum advance/vacuum_explained.pdf
http://www.lbfun.com/warehouse/tech_info/timing & vacuum advance/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.
 
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