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#4622310 - 01/02/18 10:37 PM Anybody got a dyno program? SBC build...
Alex_V Offline


Registered: 04/10/16
Posts: 1155
Loc: Campbellsville, KY
I'm doing a budget build on a 350 I got on trade, partially just for the heck of it. By the time I sell the parts that came with it I'll have gotten my money out of it, but the bottom ends looks to be in good shape. (Top end was a 10.5:1 drag setup with a 3,000-7,000 cam and mid/high rise single plane intake.) This is the first engine I've ever seriously contemplated doing something substantially different than stock with, and am curious to plug the specs into a dyno program and see what it spits out.

And if anyone wants to comment from experience on what I can expect out of what I'm looking to assemble, feel free.

Chevy 350, standard bore, 4-bolt main, cast crank
Flat-top, double eyebrow TRW pistons
Factory "480" heads: 70CC chambers, 1.72/1.50 valves
Erson TQ20H square-pattern cam: 292 adv./214 @ .050" duration, .449 lift, 111 LSA, 4* advance
Edelbrock Performer dual-plane intake

The specs on the pistons say they net 8.5:1 w/76CC chambers and 10.5:1 w/64's, so the 70CC chamber should put the compression at 9.3-9.5:1. I run 89 octane in all my stuff to begin with so that should allow me to keep that policy. This is going in my old Suburban temporarily (figure the engine in it now that runs perfect and can be demo'd will sell for more) which only needs power up to about 3,500 RPM but will do well with a lot of torque. The heads are off the original-type 327 that is my end-game engine when resto time comes along, so if I do the heads now I can just swap them over when the rest of the 327 gets rebuilt. According to spec sheets the late 60's 4 bbl. 350's (255HP) had 1.72 intake valves so I'm optimistic it will be at least decent.

Also, the timing set on the engine in question is adjustable to -4, 0, or +4. With the advance already built into the cam, should I leave the crank sprocket at 0 or advance it to bring the power down more?

Like I said, this experiment is mostly for the heck of it - can't spend a lot of money, just looking to trade some parts and play around with some spare stuff I have to see what I can do.



Edited by Alex_V (01/02/18 10:38 PM)
_________________________
I like Chevy and Valvoline.

'13 Cruze, 1.4T, 112K
'85 GMC C3500, 454, 130K
'82 Mercedes 300CD, OM617 turbo, 167K
'67 Suburban, 350, 331K

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#4622352 - 01/03/18 12:02 AM Re: Anybody got a dyno program? SBC build... [Re: Alex_V]
FlyNavyP3 Offline


Registered: 07/04/16
Posts: 1407
Loc: Jacksonville, FL
I don't have to plug it into a dyno program because I've run a lot of SBC on the dyno, by a lot I mean several hundred. Everything from stock validation engines to 2000+ HP.

Your compression is likely closer to 9:1 than 9.5 unless the block has been decked. Cam is very mild. Small intake port and even smaller intake valve will kill off a lot of power, but not torque as they just limit engine speed.

It should make 335-355 torque all in around 3300 over 300 from 1800-4100 rpm. My best guess torque number would be 345 @ 3300

It should make 240-260 HP at about 4000-4200. My guess 255 @ 4200.

For comparison a dyno validation on a 1987-1995 TBI 350 generally made 235 HP @ 4000 and 335 ft lb @ 3200 with over 300 ft lb from 2200 where we started the pull out to 4100. Those engines have less camshaft than you have but more intake valve so really that's a wash, you have slightly more compression than they have and the added camshaft duration will add a little engine speed to yours but the heads really cripple your combination for making power. The torque and drivability should be excellent.

For comparison that same validation engine with nothing more than a camshaft swap to a 230/230 .480/.480 cam and a pair of Vortec heads made 365 HP @ 5600 and 397 ft lb @ 4000, the head swap does take the engine from 8.5 to 9.5:1 compression as the Vortec head has a 64 cc chamber vs the 76 cc chamber in the swirl port TBI head. But the added airflow from the Vortec allows engine speed that's just not possible with the TBI head or the head you're using. The cylinder head makes much more difference than the camshaft in an application like this.

Nothing wrong with your combination, it's not woefully mismatched like so many engine builds I see. But with those heads it will never make big power because they don't flow enough air to make any real engine speed, which in turn kills HP.
_________________________
Luke
P-3C and P-8A Maritime Weapons and Tactics Instructor, Instructor Tactical Coordinator and Mission Commander

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#4622418 - 01/03/18 04:58 AM Re: Anybody got a dyno program? SBC build... [Re: Alex_V]
Linctex Offline


Registered: 12/31/16
Posts: 6148
Loc: Waco, TX
I agree with Luke. (GOOD Guesswork!)

Those heads are really not that great.
214 @ .050" duration, .449 lift is the the absolute max those heads will work with.

You can pick up another 30 HP or so (get you close to 280-290hp) switching to good Vortech heads.
"The cylinder head makes much more difference than the camshaft in an application like this."

I have seen some engines with very mild cams make wicked power numbers because the heads flowed well.
_________________________
"The evidence demands a verdict".
(Re:VOA)"it's nearly impossible to actually know the particular additives that are in there at what concentrations."

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#4622447 - 01/03/18 06:29 AM Re: Anybody got a dyno program? SBC build... [Re: Alex_V]
Johnny2Bad Offline


Registered: 05/20/13
Posts: 1810
Loc: Saskatchewan, Canada
I generally agree with what is posted so far. If that is enough for you, all good. They are absolutely correct in that the head, valve and cam do the most in defining power.

I have Dynomotion5, an iterative engine specifying application. It costs about $500 a license. (Iterative means it runs through various combinations ... thousands of them ... to come up with the best option as defined by the builder).

The problem with running your setup is the application requires MUCH more detail than what you've provided. For example you provide no exhaust system data. There are less advanced dyno programs ... ones that cost roughly $100 ... that can spit out information based on the simple data you've got. They may be less accurate, but can work in your situation.

The tool I have is particularly useful to generate cam timing and lift profiles that can put the power where you want; eg maximum torque at typical pubic road RPMs, RV and Tow vehicle optimal cam timing, or as crazy (and un-drivable on the street) as you may want.

One thing you may want to check out is if your state requires smog testing, generally they prohibit the installation of an engine older than the MY of the vehicle. So your setup (carb vs FI, for example) must be one that was available on that vehicle when new. Not every state or province has that limitation, but it's common.
_________________________
'57 FL Straight 50 wt
'90 Miata 1.8L w/Rotrex Supercharger [Mobil1 0W-40]
'96 Ram 1500 [3.7L Mobil1 0W-20 / 1L 15W-50]
'01 PT Cruiser [Mobil1 0W-40]

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#4622452 - 01/03/18 06:39 AM Re: Anybody got a dyno program? SBC build... [Re: Johnny2Bad]
DuckRyder Offline


Registered: 10/20/05
Posts: 4208
Loc: Atlanta
Originally Posted By: Johnny2Bad
...
I have Dynomotion5, an iterative engine specifying application. It costs about $500 a license. (Iterative means it runs through various combinations ... thousands of them ... to come up with the best option as defined by the builder).

The problem with running your setup is the application requires MUCH more detail than what you've provided. For example you provide no exhaust system data. There are less advanced dyno programs ... ones that cost roughly $100 ... that can spit out information based on the simple data you've got. They may be less accurate, but can work in your situation.
...


I have one of the cheaper versions (somewhere) and even it requires more detail.
_________________________
Robert
  • 2007 Toyota Prius Touring
  • 2005 Honda Civic Sedan
  • 1972 Ford F100

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#4622636 - 01/03/18 11:19 AM Re: Anybody got a dyno program? SBC build... [Re: Alex_V]
Alex_V Offline


Registered: 04/10/16
Posts: 1155
Loc: Campbellsville, KY
I expected a dyno program would need more info than that - just didn't go to the trouble to list it right odd the bat. If someone wants to work with me on it I can send as much info as I can gather via PM.

Thanks for the replies. I expected the 1.72's to limit it quite a bit, but that 240/345 sounds good to me for what it is. Vortec heads have value through desirability (not saying it isn't for good reason) and there's only a few factory heads with the right size chamber and any better valve sizes, so I'm leaning even more toward just using the 327 heads because they'll get redone eventually for the 327 build. If the curves peak early and fall off by 3,500-4,000 that'll be just right. The 'Burb has 3.73's and a worn out granny low 4-speed so 60 is @ 2,600 RPM and 3,500 is a real high shift. The current engine is a '78 2-bolt 350 with 624 heads, "broomstick" 300HP cam, and near as I can tell stock internals, breathing through the 327 iron intake and a Rochester 4 Jet - probably 275 gross HP at best. I'll be thrilled if the new mill can produce slightly better power through 2,500 RPM, equal up to 3,500, and get better gas mileage from the smaller valves + higher compression and torque-focused cam/intake.
_________________________
I like Chevy and Valvoline.

'13 Cruze, 1.4T, 112K
'85 GMC C3500, 454, 130K
'82 Mercedes 300CD, OM617 turbo, 167K
'67 Suburban, 350, 331K

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#4622773 - 01/03/18 01:53 PM Re: Anybody got a dyno program? SBC build... [Re: Alex_V]
Linctex Offline


Registered: 12/31/16
Posts: 6148
Loc: Waco, TX
Originally Posted By: Alex_V
and a Rochester 4 Jet


Oh goodness... I'm sorry.

I never was a fan of that carb.
It's "technology level" seemed to be superseded VERY quickly.

I've gotten 25-26 mpg from a Q-jet (set up right) on a 350 Chevy
in a '87 Trans-Am with 2.73's and no overdrive (TH-350)
_________________________
"The evidence demands a verdict".
(Re:VOA)"it's nearly impossible to actually know the particular additives that are in there at what concentrations."

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#4622897 - 01/03/18 03:54 PM Re: Anybody got a dyno program? SBC build... [Re: Alex_V]
DuckRyder Offline


Registered: 10/20/05
Posts: 4208
Loc: Atlanta
OK I found both my program and a windows box to put it on, it is DynoSim 4.11 (which is old).

If no one with a newer or better program will do it for you PM me and we will see what we can come up with...
_________________________
Robert
  • 2007 Toyota Prius Touring
  • 2005 Honda Civic Sedan
  • 1972 Ford F100

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