So I have a 1.7 or 1.8 engine in a parts car that sat for a least ten years, I picked it up last November, last time it was tabbed was 2000. I got it running, put dual carbs on it, thanks sixnot four! I got them sync'd and tuned it up and just did a compression test, the engine smokes a little when revved. #1 90, #2 85, #3 65, #4 90. This seems pretty low, I have added some marvels mystery oil hoping the rings are just a little stuck to the pistons still from sitting. I have ran the engine in the drive way for about an hour total, letting it warm up then running it up to about 2000 RPMS and holding it there for a few minutes then back to idle. My questions is should I just stuff it in my car and drive it or pull the heads, re-ring it and possibly do the heads? I'm looking for the quickest way to get a running engine in the car!

Jsaum

I say drive it and enjoyt it. start saving money for the eventual rebuild.

If the battery is good, the throttle was wide open for all of those, and the engine was warm, and you're not up over Denver, I would say those numbers are very low.

You want to see 110 PSI or more, generally. Mine were at 100 PSI and the engine was pretty well worn out.

Additionally, you want to see the numbers be as close as possible. Within about a 10% variation is generally cool. Your highest to lowest variation is 30% or more. That's also a bad sign.

If the numbers don't come up with the MMO treatment and whatever else you try, I would suggest pulling the motor. If not, then treat it as completely expendable and on a short fuse.

--DD

with DD.
I would say to check (and recheck) your valves. Poor valves will greatly effect compression. Other then that, Dave got it right. Engine warm and throttle open, compression needs to be over 100 for a driver.

Zach

I agree, NFG. It may run, but it will never tune right with those numbers.

Can a valve adjustment improve the compression numbers?

Jsaum

It may, or may not. Depends on how badly they are adjusted now, especially if they are too tight.

keith

anything under 100 psi around the block is no good?

O.K. looks like I'll be pulling the motor later this week and ordering rings! I may drive this thing yet!

Jsaum

Be careful paying too much attention to whatever nominal values you get from a pressure tester. They aren't calibrated and there are large variations among brands of pressure testers, especially as they get older. 100 lbs on yours might measure higher or lower on some other unit, so unless it's a brand new top brand the only real data you should pay attention to is the difference in values between cylinders. It appears you've got a dead one.

Yes OF COURSE adjust the valves before testing. One tight valve could mean you're pulling the engine for nothing.

The engine is currently in a parts car so I have to pull it anyway, but I'm borrowing another compression gauge and will adjust the valves and test again. A set of rings isn't that costly it's the head work that may set me back. I have several options, The engine that's in my car now I believe spun a main bearing so I could possibly use those heads if needed. Thanks for the suggestions.

Jsaum

...don,t worry