I bought my 1969 911 coupe twelve years ago. The car is quite fast and I got the reciept for the engine work.
2.4 case, head work, "S" valves, solex cams, webers, headers and a sport muffler. The paper work shows the part numbers for
2.7 RS pistons and cylinders. I've read that this 2.7 conversion gives me a 8.5:1 compression ratio.

Recently I was worried about loose head studs and I decided to take a compression check. The results are: 167 168 170 171 171 168. I don't know what the relation is between compression ratios and compression test results.

So, my question is, being that my compression test results are 170 average is it possible that I don't have the RS pistons?

This puzzles me because I've seen compression tests results on other threads and they are in the 120 range for older 911's.

Please educate me.

Thanks.