arnie

Hi everyone! First post, currently shopping for 911 SCs.

Had one on the lift today for a PPI and was wondering if someone can help me interpret these compression test numbers:
155 - 155 - 185 - 185 - 180 - 160

This is a ROW 83 SC. Both seller and I are curious about them all being high but having significant differences. 155 all around for a never rebuild engine (~100k miles) with higher compression ratio would seem fair, but strange that three are even higher in the 180 range.

Double checked the results too.

Any interpretation as far as possible would be appreciated! Hoping to join the club soon!

Spyerx

Get a leak down and find where the leakage is

arnie

Thanks! We are doing that on Tuesday, was just curious if the fact that all of them are relatively high, just not close to each other, indicates anything. I will have to be more patient...

Spyerx

Hard to say really. Leak down will tell the story. Do you know when the last valve adjust was done?

arnie

Been a while. 15-20k miles out of the top of my head. Getting the valves done before the leakdown test because we suspect that might contribute.

GTgears

How long has the car been sitting? Give it an Italian tune up and test again.

arnie

Been driven regularly and for an hour or so before the PPI.

GTgears

Then further testing might reveal a broken stud or 5.

arnie

Well looking at those numbers at least 3. ;-)

Spyerx

Adjust valves, while doing so put a wrench on the head studs and see if any of them turn. Then leak down. Listen for where the leakage is coming from.

Those numbers are bit uneven, want to see where it's coming from. And how bad.