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Old 09-24-2003, 02:10 PM   #1
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Default Compression Testing

This is continued from a previous post with trouble I have been having with the B'ville. I now have the compression gage and fittings in hand. Would some one like to share with me the correct procedure for doing the test?
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Old 09-24-2003, 07:44 PM   #2
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Default Re: Compression Testing

Quote:
Originally Posted by Dylansdad
This is continued from a previous post with trouble I have been having with the B'ville. I now have the compression gage and fittings in hand. Would some one like to share with me the correct procedure for doing the test?
Well basically there is TWO types of testing.
1) Dry
2) Wet


First for the DRY type. Unscrew a single spark plug & install your com[pression gauge connector in the spark plug hole. Now have a second person turn the engine over. read your guage, then release the pressure. Next repeat this for EVERY cylinder. when you're done you should have SIX readings. A healthy engine should have readings that are within 10% of each other (in other words the % between the highest & lowest reading should not be > 10%). If any cylinder readings are on the low side, proceed to the WET test below.

WET texting consists of eaxactly the same proceedure as above except you introduce a very small amount of ATF (transmission fluid) into each cylinder BEFORE TESTING. If any cylinder that was low before it should change slightly better now. If the WET reading goes up (better) & is now within that 10% margin above, then the rings are worn or broken. If the reading either doesn't change or increases a very small amount, then the valve or valves are worn out or "burnt" (probablly the exhaust valve).

Example: My Series I EGRless had a DRY test reading of 4 cylinders @ 120 PSI, #3 Cylinder @ 100 PSi & #6 Cylinder @ 60 PSI. The WET testing readings were: #3 cylinder rose to 120 PSI & #6 rose to 80 PSI. Therefore based upon these results, Cylinder #6 had a Burnt Exhaust Valve. Turned out Cylinder #3 had a cracked Exhaust Manifold on the outlet bend below the heat shield & hence the lower reading on the DRY test.

Hope this helps.
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