rjpbboi

How do you read compression readings? I mean like, what does say, 9:5:1 mean? Also, why is it necessary to make sure that all the valves are properly adjusted and all spark plugs are removed before performaing a compression test? And how do I make sure that all the valves are properly adjusted?

88blkbird

the best way to make sure the "valves" are adjusted is to pull the rocker covers, and hand crank the motor with the plugs out and check all of the rockers to make sure when they are unloaded that you can move them by hand. The valves don't adjust, just the rocker arms. It doesn't matter which cylinder you start with but what you should do is watch for the intake valve, when you see it closing turn until it stops rising and give it another five degrees of turn on the crank, at this point both rocker arms should be unloaded and you should be able to wiggle both of them, if they one or both are tight you need to back off the adjustment nut until you are able to move the rocker easily by hand. do this for all 16 rockers and you'll be assured set to make your compression tests. have someone help you and crank the motor while you watch the compression test until the pressure stops rising. good luck

ede

you're confusing compression reading, which is in PSI and compresion ratio which is expressed as a ratio, like 9:1. since you asked about a compression test i'll forget the ratio stuff. you want the valves adjusted correctly so there is no leakage past the valves and you want the spark plugs removed so the engine spins easier. to preform the test block open the throttle blades, install the tester in what ever hole(s) you want to test, crank the engine with the starter untill the gauge doesn't go any higher, that is your compression. the number doesn't matter much, it's more important that all the holes test within 10% or so of each other.