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Old 11-11-2003, 01:42 PM
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Pontiac Compression Test

I did a compression test of my pontiac firebird YJ 350 the other day. The motor is 30 over, has over 100k and was changed over to an Edelbrock P4B intake and a Holley 750 double pumper. I know, the carb is too much for it. The test is as follows in psi:

1-155
2-155
3-145
4-147
5-145
6-150
7-160
8-150

I was thinking of putting a hotter cam in it or just building a 400 I have sitting around here. What do you think? Is there enough power to be had here? I dont know what a good test would look like.

thanks
rob

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Old 11-11-2003, 01:56 PM
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I don't know if i would put alot of time or money in it with 100K, but the compression looks decent enough, within 10%.
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Old 11-11-2003, 02:05 PM
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Thanks for the fast response.

Even though its withing 10%, what does this compare to a fresh built 350 with...say...9:1 cr? I guess im just wondering how much I have lost over the years...

again

thanks
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Old 11-11-2003, 02:13 PM
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I can't say precisely, but I would guess at 9-1, 160's about right! Put about 3-4 good squirts of oil in the low ones and recheck em, if it comes up, the small leak is by the rings!
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Old 11-11-2003, 02:20 PM
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I'm running a 350 pontiac, with just over 50k on it, and it was always taken care of, and at nearly 10:1 compression, I'm seeing 170's give or take in my cylinders, so I'd say 160 is about right. Also, a hotter cam will wake it up, but I'd love to have a 400 "just sittingaround"! You'll find real power in that bad-boy!
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Old 11-11-2003, 02:34 PM
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thanks for the info adryan16

That gives me a good idea where it stands.

What do you think would happen if I stuck an edelbrock performer RPM cam in there? Hmmm....too much?
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Old 11-11-2003, 03:40 PM
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I think that a performer cam would be great, for either engine. I personally though, for a little novelty and after looking at the setup of the cam, ran the "068" Ram Air Blueprint cam, and think it's just awesome! It's good for a low clearance head, but has just about the max duration for a "stock" sound and driveability. Just personal preference though I guess.
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Old 11-12-2003, 12:26 AM
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The 068 is a good cam. I installed one in a 75 T/A a few years ago for a friend, 400 engine with 4x heads and it ran great, nice lope at idle and great power even with 2.79 gears. This would be the most cam I'd recommend for a low compression street engine. I have ran the Crane blueprint series cams in the past ( 041 RAIV)and after 12 years and being in three different engines I finally showed enough wear to warrant pulling it out.
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