Ring gap & head stud confirmation for 2.7

[Dpmulvan]

Originally Posted by stownsen914

I assume it's due to aircooled running hotter than the more typical water cooled applications covered in CP's published specs. I confirmed with a Porsche engine builder. This was an area I had no expertise, so I deferred to theirs.

The hotter an air cooled motor gets the more the aluminum cylinders expand. I guess it boils down to expansion rates between piston, rings and cylinders. I’m not arguing with you, I’ve got a set of these holding up a recent build and it’s sort of ridiculous that we can’t nail down numbers to go by. I guess maybe it’s worth the extra money to just stick with Mahle next time.

[stownsen914]

I also found it surprising that there wasn't more consensus on this.

As for heat, expansion, etc., the aftermarket piston manufacturers like JE and CP give different ring gap numbers for street/strip, circle track, boosted race use, etc. My application is race, so wound up using numbers closer to the "circle track" recommendations.

I also kept in mind a saying that a knowledgeable fellow shared here on the forum once:
Big ring gap = big catch can
Small ring gap = big trash can

I erred a little on the large side probably.

[PeteKz]

It will run just fine. What little difference it makes, you won't be able to feel.

[Dpmulvan]

Originally Posted by stownsen914

I also found it surprising that there wasn't more consensus on this.

As for heat, expansion, etc., the aftermarket piston manufacturers like JE and CP give different ring gap numbers for street/strip, circle track, boosted race use, etc. My application is race, so wound up using numbers closer to the "circle track" recommendations.

I also kept in mind a saying that a knowledgeable fellow shared here on the forum once:
Big ring gap = big catch can
Small ring gap = big trash can

I erred a little on the large side probably.

Any problems with rings seating or oil consumption?

[stownsen914]

Assembly is about the start. I'm hoping to be able to be able to answer that question in the coming months.

[Dpmulvan]

Originally Posted by stownsen914

Assembly is about the start. I'm hoping to be able to be able to answer that question in the coming months.

I ended up going with .018 top and .020 2nd your cp’s might be different, rather have a little blow by than seize it up.