I looked under FAQ but could not find posts about compression testing. I have a 1974 Chevy Stepside 4x4 with a 350ci. About 10 years ago it was running fine then it felt like a cylinder was missing. I basically parked it and it's been sitting up ever since.

I know I'll have to get the old gas out of the tank and clean out the line but what I need to do if try to figure out if there is one bad cylinder. I have a compression tester but I've never used it or done a compression test. I think I am supposed to disconnect the main coil wire, take out all the plugs then put the tester in each cylinder, turning the motor over for a short time, then comparing the compression numbers.

Can I disconnect the fuel line so the old gas won't get into the carb (letting the pumped fuel run into a container) or do I leave it hooked up? Since the motor's been sitting do I need to put some oil or Marvel Mystery Oil or similar into each cylinder before I test? How much for each cylinder? I do know the motor is not seized.

Also, what would be considered a "normal" compression number for a good cylinder?

Thank you in advance for any help you can give!

RP