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Old 02-27-2008, 07:52 PM
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compression testing

so I do a compression test on my 350, I get 150 all the way around, I know this is good, but why? Why wouldn't the numbers read 120, or 250? On a smaller motor like 1.7 Jetta motor what would be a good compression?

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Old 02-27-2008, 08:42 PM
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On a tired 350 with compression leaking past the rings, it could easily read 120.....or 100.....or 80 and still run, although not very strongly. A motor can operate up to about 165 on available pump gas. Over that will require race gas or alcohol or propane or whatever to prevent detonation and resultant engine destruction.
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Old 02-27-2008, 09:05 PM
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Hey Gladis,
Go to wikapedia (what is static engine compression) and all your questions will be answered in simplicity,that is until you see the algebraic equation for mathematically explaining it.
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Old 02-27-2008, 09:06 PM
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over all a cylinder leakdown test is a better way to determine how your engine is going to run. another way to find the condition of the engine is through the vaccum, if you google it you should be able to find infrmation (i lost the page my instructor gave th class on translating vaccum readings into solid diagnosis)
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