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Dry compression test outside of car

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Old 04-16-2010, 03:41 AM   #1
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Default Dry compression test outside of car

A local seller has a 2000 LS1 for sale that I am interested in. It is currently sitting on an engine stand, and has since he bought it (receipt says 6/2009). He bought it from a Corvette parts business and the receipt shows he paid for a 01' Camaro engine with 67k miles. I checked it out and it has 241 heads and a pre-01 LS1 intake manifold which leads me to believe it is a 2000 model year. Since the place that he bought it from lied that it was from a 2001 car, I can't trust the mileage that they gave him.

I want to do a compression test to see what kind wear and tear is on this engine. My question is, since the motor has been sitting for likely over a year without any oil, is it a bad idea to turn it over? I was thinking of getting the engine on a hoist and putting the flywheel on, then jumping the starter terminals with a spare battery. Would it cause any damage to the bearings/hydraulic lifters/oil pump to do this for a short amount of time, having sat for this long and having no oil in the pan?

And what compression numbers would a strong motor produce?
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Old 04-16-2010, 04:11 AM   #2
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Do a leak down test instead. We leak down all our engines we build on the stand. Its a better way to see the integrity of the engine than a compression test. Also a compression test really can't be done on a cold engine.
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Old 04-20-2010, 05:46 PM   #3
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I ended up buying that setup. It was a great deal so even if I have to do some rebuilding, that's fine with me.

I order a leak down tester from Harbor freight for $40, it should be arriving today or tomorrow. Are there any write-ups to the procedure? I've looked around but haven't found anything too specific. How do I find TDC for each cylinder? And will I get better results if I pull off the rocker arms to make sure each valve is seated fully?
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Old 04-20-2010, 09:04 PM   #4
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This should help.....http://www.carcraft.com/techarticles...ter/index.html
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Old 04-22-2010, 02:47 AM   #5
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Would there be a large variance between doing a cold leak down test and doing one with a warm engine? I know the metals will expand and help with sealing when warm, but just how big of a difference does that show on a gauge? I am getting unacceptable leakdown percentages (%30+), but the engine is cold since it is out of the car. All of the leakage is past the rings and I can hear it in the oil fill tube.
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