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Hello guys....
What compression test readings are considered okay for a '75?
Thanks,
Al
What compression test readings are considered okay for a '75?
Thanks,
Al
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Re: Compression test readings
Actual compression pressure readings can vary significantly from published CSM specs. Deposit buildup and gage accuracy play a role.
The important issue is that all readings be in a fairly narrow range. If all are within 10 psi, the engine is probably healthy. The OE limit for variation is 20 psi.
Make sure you remove all spark plugs, remove the HEI power connector, block the throttle wide open, and crank until the gage reading peaks, which is usually 4-5 cycles, and the engine should be at operating temperature.
Duke -
Re: Compression test readings
Thanks Duke. The carb is off and the dist. is disconnected. I'll pull all plugs and test with 5 or so cycles and check readings. Thanks for the help!
AlComment
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Re: Compression test readings
Without a carb, you obviously won't be able to do the test at opearting temperature. Cold readings are usually lower and might have more variation.
It's also a good idea to get two full sets of data as a consistentcy check, especially if some read low.
If any cylinders are low, use an oil squirt can and a couple of pumps into the top inside (high point) of the cylinder through the plug hole. Then run a couple of more tests. If the pressure comes up, the rings are probably the problem. If not, a leaky valve is probably the problem.
Post your results for an analysis.
DukeComment
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Re: Compression test readings
Will do. Thanks Duke.
Regards,
AlComment
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