oil in my heat exchangers and pre-silencer

[svm]

I have a porsche 911 3.0 SC Targa (1979). I want to do a complete renovation of the car.

I dismanteld the silencer and I saw that there was a lot of oil in the pre-silencer. It comes from a heat exchanger.
I took the compression off all 6 cilinders and they all have 7. I think it's a bit less ?
My opninion : Its the valve-seals or the pistonrings.

Is there anyone with the same problem ? Is there anyone who can give me a few tips. I am a mechanic but It's my first 911 so I don't have alot off experience with the car.

Thanks !

[svandamme]

hi SVM, as i suggestd on the Dutch forum
couple of books that are well worth buying
- Bruce Anderson , 911 performance Handbook, lists all variations of the aircooled engine and it's components
- Wayne Dempsey, How to rebuild my 911 engine,
step by step information and tricks one how to get it done
Wayne is the owner and CEO of Pelicanparts, and big kahuna of this Forum

i'll leave it to the others to comment on possible causes, i think Valve Guides
which seems to be a likely cause considering you mentioned in the dutch forum that after wiping things clean, you (relatively) quickly found an oil drop forming near the Valve and Guide on one Cyllinder head...

plenty of folks here that can offer more experienced rebuild advice then i can at this time

either way , welcome on the board !