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cold leakdown test=bad readings?

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Old 03-09-2006, 11:32 AM
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Default Help/opinions on my leakdown test

I did a leakdown test on my engine while I was waiting for my new pushrods. I did the test with the rockers off and a cold engine. I got between 19 and 21% across the board while i know thats high im wondering if anybody has done the test with a hot and a cold engine and how much less the leakdown will be when its hot. It will be at least another week untill i can start the car again. I have known from the start with this engine that there was an issue with blowby. It was pushing oil into the intake. I tried the ls6 valley cover the catch can then i realized it was pushing the oil into the intake through the line off of the valvecover thats supposed to be the inlet for fresh air into the engine. even at idle the pcv doesn draw enough air to keep the crankcase at a negitive pressure. I then went to the breather on the valve covers which solved my oil in the intake but oil would come out and fall on my headers. So i ran a hose to the breathers away from the headers so hopefully it wont smoke after every pass from the oil on the headers

Last edited by koolrayz; 03-11-2006 at 08:54 AM.
Old 03-09-2006, 02:27 PM
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I leak tested my stock LS1 from a 99 C5 when it was cold and it was 3 or 4% on all cyls. My race motor with more ring end gap was 5-6% after break in. If you are doing the test right, and your gauge is accurate. I'd say that your motor is worn out.
Old 03-11-2006, 08:50 AM
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Its a brand new tester. Im sure the readings are right. It would explain the high crank case pressure. What sucks is this engine has less than 4,000 miles on it and has had the symptoms of high crank case pressure since it was new. I called and talked to the builder last week and he told me to take the readings again warm and it would go down to 10% and that would be OK I say thats bullshit it wont go down that much and 10% is to high.
Old 03-11-2006, 01:17 PM
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Rings
Old 03-11-2006, 02:57 PM
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d bet the Rings were not setup properly or maybe they didnt seat correctly....Are you blowing the dipstick out of the tube at little at WOT. I bet you are burning a TON of oil....
Old 03-12-2006, 02:23 PM
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hasnt blown the dipstick out yet. I think it was a setup issue with the rings from the builder. I had the ohio boys do the engine install for me they did the startup and seated the rings. they are no strangers to high performance engines. swapping the engine was to much to do alone on jackstands. They do great work at very resonable prices.
Old 03-12-2006, 08:29 PM
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Originally Posted by koolrayz
hasnt blown the dipstick out yet. I think it was a setup issue with the rings from the builder. I had the ohio boys do the engine install for me they did the startup and seated the rings. they are no strangers to high performance engines. swapping the engine was to much to do alone on jackstands. They do great work at very resonable prices.
I agree. In that case I wouldnt expect it to get any better....sorry man.
Old 02-22-2007, 10:33 PM
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Before pulling the heads on a 04 ZO6 to do a cam & ported head swap, the leak test results were 3-4%. This was on a cold engine with 7000 miles.

Russ Kemp
Old 02-22-2007, 11:08 PM
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I believe a method of determining if it's actually your rings is to squirt a bit of oil in each cylinder. Supposedly if the % lowers than there's a better chance it's your rings at fault.
Old 02-27-2007, 12:54 PM
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i know this is kinda "old" but i did a cold test on my car yesterday after spinning the stock engine to 8000rpm..

4 pistons were showing 9%, and other 4 were at 20%.. I indeed was sad.. Then, after playing with piston position a bit.. all cylinders were cool at 9%...



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