I got a compression tester and this is how i check the compression. I removed a spark plug and installed the gauge. I then cranked the engine over until the gauge popped up. All of the cylinder ran about 115-125 psi. The motor is a 455 olds stock with low compression piston. Rebuilt about 15 yrs ago (boat was given to me) The motor runs good with ok power for a stock motor. I am pulling the motor on friday to have intake replaced. Did i run the compression test correctly? If not how do i do it correctly? Are those numbers okay or should it be higher? I need to know if i should pull the motor down or not while it is out.
Thanks :eat:
Remove all the plugs and check it with the carb at WFO. The number itself isn't as key as having all the numbers within a few percent of each other. There are a lot of variables that will affect the number so don't sweat it, unless they're all in the single digit range, then you have problems.
Sounds about right for low comp. pistons. If its running ok, why mess with it. Also, why pull the motor to change intake?
Engine should be warm also.
One question I have - what percent leakage is typical/acceptable for a fresh engine?
Brian
.....Also, why pull the motor to change intake?
I believe he is having the PUMP intake replaced.
Buy leak down gauge.
If you do recheck the compression with the throttle open, try to only open it once and keep it there so you don't keep squirting gas in it. Your results would probably be even worse than before.
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