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Compression Check

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Old Feb 6, 2011 | 01:27 PM
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Default Compression Check

Can you do a cold compression check if yes whats good numbers for an LS1?
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Old Feb 6, 2011 | 04:04 PM
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Yes you can do it cold, I normally let it warm up, and then do one side, warm up again, then the other, just waiting for it to cool enough to do it. However I have done many when cold too.. My manual says minimum 100 psi. with a maximum variant of 25% from the highest reading. Hope this helps
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Old Feb 6, 2011 | 04:31 PM
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thanks motor is out of car so I have no choice
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Old Feb 6, 2011 | 04:46 PM
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i did mine cold and got numbers from as low as 4% and as high as 17% so u can do it cold
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Old Feb 8, 2011 | 09:07 PM
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I checked one side and got just over 50psi on each cylinder then I checked other side and was getting just over 75 psi on each cylinder so I checked first side and it was higher just above 75psi also. I think from spinning motor I was helping rings seat better, what do you guys think about the cold check at 75psi it was consistant throughout.
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Old Feb 9, 2011 | 10:06 AM
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I think those nubers are awful low, You are using the starter to turn the engine over right,, If yes then that engine is way on the weak side and not building much cylinder pressure at all. I would suspect rings myself considering all the cylinders are low. being cold dont make that much of a difference any way,, might want to get another compression gauge and take the readings again. PS its easier on everything if you go on and remove all the plugs when doing this considering its out of the car.
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Old Feb 9, 2011 | 11:32 AM
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Originally Posted by RARON455
I think those nubers are awful low, You are using the starter to turn the engine over right,, If yes then that engine is way on the weak side and not building much cylinder pressure at all. I would suspect rings myself considering all the cylinders are low. being cold dont make that much of a difference any way,, might want to get another compression gauge and take the readings again. PS its easier on everything if you go on and remove all the plugs when doing this considering its out of the car.
I did have the plugs out, but I was turning motor over with a ratchet
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Old Feb 9, 2011 | 07:12 PM
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Bolt up the starter and use it, or find someone with a leakdown tester...
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Your the MAN!
Turning it manually fast enough to get gauge readings!
Bolt up a starter and check but I think you'll probably be fine.
Been wrenching since 1980. Don't remember ever seeing anyone do it by hand.
Starter should spin it over 250-400 rpm. You'll get MUCH better (both higher and less deviation) readings at this speed.
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