Just bought a 97 2500 ram truck after doing a compression check i found that cylinder 8 has nothing. The truck runs just misses here and there.I would think if its a bad piston or rings it would start coming apart,the guy told me hes driven it for two weeks like it is and wasnt sure what was wrong. I found it while doing a tune up. could it be a bad intake valve and all the compression is going out the exhaust? the rocker arms move up and down for that cylinder.

With #8 at TDC, pressurize that cylinder with compressed air and listen for where it is escaping. Through the carb/throttle body - intake valve; though the exhaust pipe - exhaust valve; through the breather - bad/broken rings or piston; bubbles in radiator - blown head gasket. That should narrow it down Just be careful if it is not at TDC the engine might turn over (watch fan blades/pulleys) although with no compression it may not be a problem.

Ok i'll try that. I never thought of a blown head gasket. but i guess anythings possible..thanks