stock compression questions

[386kustoms]

2 questions for me the newbie. first off also i have searched but dial up is a pain in the ass lol

question 1 why should a car be at operating temperature to do a check. if the car is cold would the numbers be lower or higher?


question 2 i have a stock 84 hot air. i did a check while the engine was cool because i am waiting on some parts so i can keep it running. i got numbers from 125 - 140 what should the numbers be on a stock block. i think i read somewhere that 140 was good so if i had cyl between 125 - 140 is that still ok ?

 

[386kustoms]

anyone????

 

[Quick6'n'-K.C.]

Ive never done it hot, whats the point you burn yourself?

I was always taught to do it with the throttle body open and the numbers shouldnt vary too much, yours is down if it only shows 125 in a few cylinders.

If thats the numbers, you might have alot of carbon buildup between the valve and seat. Id air the cylinder up and check to see if you have leaks up or down(intake or exhaust) air leaking past the valve. Listen for air coming up thru the intake or down thru the exhaust manifold.

If you do, remove the valve cover and rap the top of the valve to see if it clears up when you still have air pressure on the cylinder, it will blow out the carbon one way or the other.

Ive done this on alot of high mile motors, the carbon builds up pretty bad and the valves dont close all the way
BW