I did a compression check on my car just to make sure everything is ok. I am not sure however if these are good reads. I was wondering if someone could help me out by telling me if these results are good or not. cylinder # PSI 1 110 2 110 3 110 4 110 5 90 6 115 7 110 8 100 i am not to sure about that drop with the #5 cylinder and the #8 . I ran the test serveral times on those cylinders and repeatedly got 90 and 100 so I guess thats what they are.
Hi David, Well, it depends on exactly what is done to your engine, or if it's stock! For a stock engine that would not be bad, perhaps the rings are worn a little. On the other hand, i know that some years of 302's had taller deck heights and would have lower compression--i'm not sure what years or if your engine would fit in that category, but if that were the case then those would be perfectly good numbers. As for the two low cylinders, you could try squirting some oil into those cylinders and testing again. If the compression goes up then you have worn rings if not then perhaps a valve is not completely seated. You might want to consider runnign something like Marvel Mystery Oil in the oil for every oil change, i have heard a LOT of success stories using it and after tearing down my friends 350 with 320,000 miles--i'm a believer!
The comparison of the cylinders is more important than the number itself (within reason). They should all be within 10%. #5 cylinder is out of range & #8 is on the edge. Only way to tell for sure is to pull the head. As long as the car is running good, I wouldn't worry about it.
