ronone10

I have a question about the results of the leakdown and compression tests on my '93 C2 that has 68k miles. I am curious about the compression numbers being low even though the leakdown in all cylinders is between 1-4%. The compression numbers are:

1 – 165
2 – 165
3 – 178
4 – 155
5 – 160
6 – 175

The C2 is almost 2 weeks old for me and I have zero problems. Are the compression numbers within an acceptable range? Any reason to be concerned about #4 being at 155?

Ok, a dumb question but how much of a performance drop is there with lower compression numbers? Such as 0-60 time..

How does it compare to a new '93 C2? What are some reasons for the lower compression numbers?

Can you tell this guy is new!!!

Thanks

Ron M.
C2 '93 Guards Red

Gary R.

I wouldn't be the slightest bit concerned. Enjoy her!

ronone10

Gary,

Thanks for the vote of confidence. I added a few more questions to my original post. But you are right, I should just relax and drive her...

Ron
C2 '93 Guards Red

mxbanker

I have seen higher but as long as they are within 15% of each other you should be ok. Have fun with your car- I drove a 71 that had "low compression" for 175000 miles!

springer3

The compression test is not as reliable as leak-down. Leak-down results are more reliable because they don't depend on:
1) cranking speed
2) the number of compression strokes used
3) ambient air temperature, humidity, atmosphereic pressure
4) engine temperature
5) oil viscosity and temperature

Consider that the compression test is done at cranking speed, perhaps 400 RPM. You will be turning over 4000 RPM when you are making peak torque and power. You are leaking very little at 400 RPM, so at 4000 RPM the leakage is negligible. There may be a small performance reduction, but at the compression values you are getting, it is not measurable.

Don't check compression unless you are prepared to perform major engine surgery. If the car is driving great, all the compression test can do is ruin your day if you find a problem. I agree with the advice to drive and enjoy.

Bill Gregory

I like to see both compression and leak downs together, in the event there appears to be a problem. With leak downs of 1% to 4%, the engine is in good shape, so, as others say, enjoy it.

ronone10

Everyone, thank you for your input and advice. I definitely will enjoy driving her. You all already know this but this forum is fantastic.

Thanks again..

Ron
'93 C2 Guards Red