I was reading further up in the thread about calculating compression rates from PSI and while this can be done is a broad cense it does not work all that well due to cam timing.

I totally agree about the weirdness! Its a second hand 944 whithout any id on the engine. The previous owner told me that its not its original but the look is the same. To which engine are these rates close to? Could it be a S engine with a na head ??

Look at the temp sensor on the head (for the gauge) Small one is pre 85.5 Large one is post 85.5 Not definitive but a good start. I think somewhere on Clarks garage there may be a casting number list you can look up your block number as well as the head casting number and get a better idea as to what the motor really is. I mix and match NA motor parts a lot when rebuilding. I usually take 83 bottom ends and use 89 heads and cams.

Hello Dean, thank you for your help!

Head part number: 944 105 250 6r (did not find any conclusive result, maybe from an S)

Bell Housing part number: 944 116 401 2R (seems to be from a turbo!)

The temp sensor looks small though.

87 944 na

1 - 150 - 155
2 - 160 - 165
3 - 155 - 160
4 - 150 - 152.5

1 - 183
2 - 185
3 - 190
4 - 190

84 na

155
165
165
165