Dry test is when you just do the compression test by taking out the plugs and hooking up the tester. Wet test is when you spray say WD-40 or use a teaspoonful of oil in the combustion chamber. What it does is to seal the rings. If your compression goes up significantly, you have a bad set of rings. If it doesn't, the problem lies in the valves. You can also do a leakdown test to see how much leak and more importantly where it leaks at.

IMHO, if it goes up too much with the wet test, it tells me that the rings are the problem. Talk talk to a machine shop and ask them how much is too much.

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