Thread: 350 engine compression testing

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The advice given by both Ken and Tech is spot on for a true compression test to determine the overall health of the engine, but you're looking for a dead cylinder. If it were mine I think I'd pull the plugs and squirt about a tablespoon or so of Marvel Mystery Oil in each hole and let it sit for a day or two, just to get some lube on those dry cylinder walls. Since you know the gas is bad, and the tank & lines need to be cleaned out unhook the line at the inlet to the pump and shove a golf tee into the line, and while you're at it take off the line from pump to carb, too since it'll be coming off to clean, anyway. Then wire the throttle open and crank it like Tech explained. Don't worry to much with the value of the compression number you get, but look for consistency between holes, all pretty close to the same. If you have one outlier you know where to look for your problem.
Once you have your problem identified clean out your fuel system, fire it up and follow Tech's process to the letter to know where you are for engine health. Just my $0.02 on chasing the unknown.

Thanks VERY much, my 3 amigos!

I am printing your instructions out so I'll have them handy when I test.

Best,

RP