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get a leakdown guage via summit and remove all the sparkplugs from the holes, hook the guage up to your air compressor and inject 100 psi of air into each cylinder at its TDC, you can find tdc by injecting say 20psi and listening for TDC or also its right after the crank gets super hard to turn to super easy. Once at TDC inject 100 psi, look at the 2nd leakdown guage on the tester. if it says 90 then then that cylinder has 10 % leakdown. Also you need to listen to where it is leaking from. If it is going into the oil pan you have blowbuy IE ring/pison issues. If it is out the intake then your intake valve is fuxored. Likewise if you here air escaping out the exhaust its your exhaust valve. If you see bubbles in you coolant than you have a head gasket issue. Its a really cool test to do especially being able to hear wear the problem lies. Also anything above 10 % is real bad, 7-10% is still bad but ok. 4-7 is pretty damn good. Under 4% and your leakdown % is rivaling race cars. I could be wrong slightly on the above % but basically anything up to 10% is ok with 9 and 10 % being iffy.


A leakdown test will test for leaks in both the intake and exhaust valve as well as the rings. With the rocker arms off, both valves should 100% sealed. Some blowby (less then 5%) is acceptable and most likely coming through the rings. If an intake or exhaust valve was leaking, it can be heard through the intake or exhaust system. If both of those are good and the leakage is greater then 10%, the rings are wooped! I would also do a cylinder cranking test as well to add to the testing results!

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Hope this helps some of y'all

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Florida SS buff
Now in Newport/Middletown Rhode Island
2002 Bright-Red Firehawk # 35.
M-6, Loaded to the hilt
315 hp/335tq as of March 14, 2004

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