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Built 1.8 Motor - What should my compression results be?

Old 01-17-2012, 02:03 PM
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Default Built 1.8 Motor - What should my compression results be?

Hey guys - So I'm running a 1.8 with CP 9:1 pistons and I'll be running a compression test after about 800 miles of break-in/beating-the-****-out-of-it.

What should I see for numbers? Clearly it will be lower than factory but is there a way to determine the numbers, or does anyone just know them? What are you getting with your healthy 9:1 built engine?

Thank you!
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Old 01-17-2012, 02:18 PM
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Gauges will all read a little different, so just try to look for variance and not so much a raw number.
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Old 01-17-2012, 02:20 PM
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You're looking for consistency, not a set number. If they're within 10% from lowest to highest, you're good.
Obviously the closer together they are the better it is.
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Old 01-18-2012, 10:40 AM
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Results 150 149 150 150. I'd say that's good. Break in successful!
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Old 01-18-2012, 11:25 AM
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Very nice!
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Old 01-18-2012, 11:36 AM
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Now leak it.
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Old 01-22-2012, 03:10 PM
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how much leakage % is acceptable?
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Old 01-22-2012, 03:17 PM
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Originally Posted by muoto View Post
how much leakage % is acceptable?
On a brand new motor, 3-5%.
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Originally Posted by codrus View Post
Basically I've come over to the camp of "If something is a reliability problem on the track, just ask Andrew and do what he says".
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Old 01-23-2012, 02:19 PM
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Old 01-23-2012, 02:34 PM
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Bro, that 710 cap is tight. Come at me.

That looks good, now leak it.
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Old 02-14-2012, 05:53 AM
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Quick question for you guru's (especially Savington)
I made metal plate between head and block so I can measure my valve leakage %
Results were:
cyl1 = 2% leakage
cyl2 = 6% leakage
cyl3 = 2% leakage
cyl4 = 2% leakage

should I do something to that cyl2 (slightly leaking exhaust valves)? When my engine was warm I got 190 psi compression from that cylinder

cylinderhead work here is expensive
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