Hey dirt reynolds,rick wi,lowend,rist bucket 79, and eric 68, I was able to do the compression test this morning on the 383 stroker vortec setup and hers the results.
cyl 1. 192
cyl 2. 195
cyl 3. 195
cyl 4. 190
cyl 5. 195
cyl 6. 195
cyl 7. 195
cyl 8. 195
I hope this helps you guys with determining what would be a correct and good cam for my motor. If you need anymore info please let me know.
Thanks Mark

Those are outstanding numbers! Excellent balance and perfect for pump gas.

What cam you have in there with those numbers?
I know its gonna sound funny but all i have is 140 unless the guage i used was broken?

http://www.supermotors.org/registry/vehicles/showmedia.php?id=163599&original=1

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1972 Camaro 350 factory heads 1.94/1.5 street driven full interior
93 octane everything works 7.59
89.54 mph
Never owned a trailer never will!

thanks 1978 lt. I don't know quit what they mean, I hoping dirt reynolds and lowend and the others can explain what it means and what to do next.

m wilson the cam is a comp cam part no. 12-502-5

Those are nice numbers.I have a feeling you need a 10in. converter if it's a stone out of the hole.

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1978 Z-28 purchased new by me -$6750
Click here (http://f1.pg.photos.yahoo.com/ph/someonehasthisid/detail?.dir=/d752&.dnm=aefd.jpg) to view present state photo
Look above for glory days.
1994 Formula
1982 350 S-10

I wouldn't change the cam if I was you and if it's a streeter. You need 3.42 or better gears, and atleast a 2600 stall converter.

The cranking compression is based on...

The compression ratio of engine (head cc, bore, stroke, and piston cc) and the cam size...

Bigger the cam, the more pressure it bleeds off, the smaller the cam the more pressure it leaves in the cyl.

The gen idea for a good performing street engine on pump fuel is 185-195 psi with 200 being max

Your #'s are right on target for a hot street engine.

Nice balance between all 8 cyl. shows you have good ring, and valve sealing in all 8.

To give you some idea's on cyl. psi on diff engines....

My 10.18:1 355 with a 278/284 216/228@.050" cam with 112 lsa gives me 217-219 psi across the board.

That's alittle much for a safe streeter. I have to keep my timing dailed back to run on 92/93 octane fuel.


Cyl. pressure

Stock engines....

1966 396 375 HP 11:1 160 psi

1969 DZ 302 11:1 190 psi

1964 427 425 HP 11:1 150 psi

1969 350 370 HP 11:1 190 psi

Chevy high performance's test/Modified engines....

355 9:1 224@.050" (IVC @ 60* ABDC) cam 180 psi

ZZ4 350 10:1 208@.050" cam 195 psi

355 8.75:1 224@.050 (IVC 60* ABDC) cam 140 psi

HT 383 9.1:1 196@.050" hyd. roller cam 195 psi

HT 382 9.1:1 XRE 282 cam 230@.050" (IVC @ 67* ABDC) 185

Numbers look like you're in the area of 10 to 10.5 to 1. As far as camming now it comes down to what you want to accomplish. A smaller cam will give you more lower to midrange power. A wider lobe separation will help with your brake issues and coupled with the smaller duration will allow you to keep your current compression.
It all comes down to what you want to do. Personally, I think you have a bunch of tuning to do to optimize what you currently have before you look back into the engine. Your cam is a little large but you should be able to work around that.

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Custom Auto, your source for quality machine work, cores and new parts at competetive pricing right here in British Columbia 1-888-563-4050
A Canadian, EH? (with a 10 second street car)

According to my book you're right at 10.0 compression, maybe just a tick under or over depending on camming.

I don't know how accurate getting true static compression ratio from a compression test is. I get 210PSI and I only have 9.5 +-.2 CR. Short 268/272 cam however makes cranking compression real high.

And there exist a multitude of weather variables (altitude, density, etc.). Hard to get a close reading I would think.

What I'm looking for is a setup that's more tuner freindly. What I mean is the cam I have now, I can't get it to stop pinging, even with 94 octane gas. It doesn't idle at all until after running for 5 minutes. Should I change carbs? I was thinking of getting a edelbrock and get ride of the holly p[ro systems carb.

The Vortec combustion chamber should be able to make those pressures driveable on 94 octane with any cam over 220 @ .050.

redcamaro72.. You have probs in other places.

I have 1966 iron heads, 217-219 psi cyl pressure and can run 34* total timing on pump 92/93 octane fuel without pinging any.

I do have a 2800 stall converter that helps to keep from putting the engine under load at low rpm.

Get use to the 5 min warm up on a hot rod. I don't think I have ever seen a built carbed engine that can crank up and go within a few seconds like a new car can.

Even with a choke it will take it a min or two to get where she'll idle right when you leave.

My warm up goes like this.
pump throttle 3 times, start engine, bring RPM up to 1500 and hold for about 45 sec., rev to 2500 2-3 times, let rpm fall down to 1200, and hold for about 2 min. Then take my foot off the throttle easy and she'll idel fine.

If I need to leave in a hurry, I just two foot it, left foot on brake, right foot on gas and go


As for as your pinging.... What quench height did you build into the engine (deck height plus gasket thickness)?

What spark plugs are you running? I had to drop back 2 heat ranges colder (from R45's to R43's) to keep from pinging

Whats your timing curve look like?

Where does the mech advance start advancing, and where does it stop (RPM wise)

What about you vac advance. Are you useing a stock can or one with a lower vac point or adjustable one?

Whats your total timing?

What about your jetting.. How you got the carb jetted. If it's lean it will ping. I had to go 8% richer on my edelbrock 600 cfm man. choke

What about water temp? how hot does she get

Air temp. Is the carb breathing in hot under hood air?

You need to set your timing curve to start advancing at about 800-900 rpm, and be fully in at around 3,000 rpm (if you still ping you may need to slow it down and let full advance come in at 3300 or so)

Set total timing at 32* and work up from there till you ping, then go down a degree or 2...


You just got some tuning bugs to work out. It took me 3 mo. to get all the bugs worked out of mine and get everything dailed in. By spending that much time one tuning I went from a pinging mid 13 sec car down to a great running drive anywhere mid 12 sec car

In addition to some of the excellent responses already posted, eliminate the vacuum advance and set total timing at 30 degrees to start and adjust up or down as required. Sounds like you'd enjoy the cam if you could eliminate the pinging. You may have to richen the mixture screws and jets to help with the pinging as well.

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Custom Auto, your source for quality machine work, cores and new parts at competetive pricing right here in British Columbia 1-888-563-4050
A Canadian, EH? (with a 10 second street car)

Night rider. I have no clue on the quench height. my spark plugs are r44lts. my stall converter is around 2800 also. I haven't played with the timing too much( I'm new at this just put a msd setup in her, dist. wires,6a box)Its starting to get cold here in Pa so not much time to get everything done. Can you explain what I need to do for the timing aspect in details?

redcamaro... Your prob is in your last post. "I haven't played with the timing too much" and "just put a msd setup in her, dist. wires,6a box"

The parts are great. No prob with that. It's the tuning of them.

Timing is one of the biggest causes of pinning.

The total timing is the intial (the 8, 10, 12* BTDC you always hear) + the mech. timing. The mech, is the center plate and weight setup.

The timing curve or advance rate is the springs and weights

lighter springs brings mech. timing in faster. If all the timing comes in too fast you'll ping, or if total is set too high you'll ping.

To check and set total timing you'll need 1 of the 3... dail back timing light, timing tape and reg. light, or degreed damper and reg. light


Shoot the light at the damper/timing tab. What you see is the intial timing.. Now rev engine in 500 rpm steps and write down the degrees at each 500 rpm

go from your idel intial, to 800, 1000, 1500, 2000, 2500, 3000, 3500, 4000.

The timing degrees will move up as you go. At the point it stops moving is where your total timing is fully in at.

Like my timing curve looks like this...

Initial timing 600 rpm 16*
800 RPM 22*
1000 RPM 25*
1500 RPM 27*
2000 RPM 28*
2500 RPM 29*
2800 RPM 32*
3000 RPM 34*
3400 RPM 34*

There's debats on how to set timing. Myself I go with the don't worry about Initial and set total, and rate of advance.

If I needed my timing to be fully in later, I would swap to a stiffer spring., If I needed it to be in sooner I would do to a weaker spring.

There's no one right answer on what to set timing at. Every combo is diff. You'll have to play with the rate of advance and total, till you get it to stop pinging.

Gen guide lines are 30-34* total with vortec heads, 34-40* with older style chamber heads.

Timing fully in at 2800-3200 rpm

Read over the papers that came with your MSD dist. It should tell you how to change the springs and all for the rate of advance

That's a good cylinder-to-cylinder balance on the compression test. With iron heads it is on the high edge of OK for pump gas. If your quench is set up good, timing curve is reasonable, and coolant temp is kept low you should be fine as is on pump premium.

You probably could go one size bigger on your cam, but you didn't mention what cam you already have . . .

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Mid 11's on pump gas, all motor . . . and no trailer.