Johnd

Well a few weeks ago, I borrowed a compression tool from a friend and the readings came back between 140 and 160. So I went out and bought a new compression tester (craftsman model). I tested again today and below are the readings:


1 150
2 150
3 160
4 150
5 155
6 150
7 160
8 150 - this one was a pain in the *** - came in at 140 - after tightening the hose it came in at 150


I tested with the motor cold - so do these numbers seem good?

MDchanic

They look fine to me, though you're supposed to test it hot.

Did you do it with the throttle open?

- Eric

Johnd

Hi Eric,


I was told it could be done on a cold engine but the readings would be lower. There is no way to do cylinder 8 on a car with AC when the engine is hot. It took me 15 minutes to connect it cold

crank shaft

Make sure you hold the throttle wide open and do 5 puffs when cranking. You should not have more than a 20 percent variance between cylinders.

MDchanic

And, according to the numbers above, the maximum variation between cylinders was 10 psi, a 6.7% variation.

- Eric

crank shaft

Yes. Thanks for the correction!

Johnd

Guys,


Thanks for all the feedback... So would you bother ripping it apart or just do a rebuild of the top end and replace the gaskets

matt69olds

The textbook process is to warm the engine, disable the ignition, and remove all the plugs. Do the test with the throttle wide open.Crank the engine the same amount of time, and make sure the battery is in good enough condition to maintain constant cranking speed. As long as the numbers are consistent, within spec and within 10% highest and lowest your probably OK. A leakdown is more accurate for determining overall engine seal condition.

MDchanic

You've got great numbers there. Why do you want to mess with the engine?

- Eric

Sugar Bear

X2, those are excellent numbers. If it sounds good...no knocks, taps etc. leave it alone except for the timing chain. If the chain or gears are old then change the chain and both gears.