Compression test result questions
Thread Starter
Racer
Joined: Aug 2001
Posts: 401
Likes: 22
From: SF CA
Compression test result questions
Does anyone know a reference book for these results? I know it's important that they be within 10% of each other but I didn't know they could be this high. It is an L-88 motor, I believe the compression ratio is 12:1 or 12.5:1.
1 212
2 220
3 218
4 220
5 216
6 210
7 214
8 208
Thanks
1 212
2 220
3 218
4 220
5 216
6 210
7 214
8 208
Thanks
Team Owner
Joined: Aug 1999
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SPARTAN
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Re: Compression test result questions (BAD-L88)
They look good to me.
The pressure is a function of 2 things. The compression ratio and the camshaft. A long duration, high overlap camshaft will create lower cylinder pressures during a compression test simply because the valves are staying open longer and are letting some air out on the compression stroke with the low crankig speeds.
I think you'll find that many others here have high pressures like that too. But everything looks good so far.
Dave
The pressure is a function of 2 things. The compression ratio and the camshaft. A long duration, high overlap camshaft will create lower cylinder pressures during a compression test simply because the valves are staying open longer and are letting some air out on the compression stroke with the low crankig speeds.
I think you'll find that many others here have high pressures like that too. But everything looks good so far.
Dave
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
Re: Compression test result questions (BAD-L88)
They look good. My 11 1/4 motor was 180-190. The cam has alot to do with the cranking compression. I usually do leak down tests.
Norval
Norval
Drifting
Joined: Nov 2000
Posts: 1,361
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From: Honolulu Hawaii
Re: Compression test result questions (BAD-L88)
Healthy. Very healthy!!
In David Vizards book titled something like Max Performance Build for Small Block Chevys on a Budget, he gets into cranking compression readings and ranges. He says 200 is good street numbers and 220 is good street/strip numbers. Do you run on pump gas?
In David Vizards book titled something like Max Performance Build for Small Block Chevys on a Budget, he gets into cranking compression readings and ranges. He says 200 is good street numbers and 220 is good street/strip numbers. Do you run on pump gas?
