Dropping C/R on 993 engine
 

I just got done talking with Charles @ LN about pistons and reconditioning my mahle barrels.

So my question is .... Is it worth dropping the C/R down from the 993 stock 11ish to say 10.5-1 or just get the 11.5-1 JE pistons he has in stock? Seems that >11 CR isnt going to work with carbs running 93 pump gas. I am still going to run PMO carbs. Im not sure how much timing I can retard to make it work but dont want to loose too much power. Hoping that Henry or Steve chime in.

Thanks

If it were me and wanted faster replies. I would post the inquiries on Steve's Rennsport forum.
Good luck with your upgrade.

What forum is this .. Ive never heard of it?

Surf Steve's website for info.

Thanks ... been on the site before but never saw this part.

If you actually measure your motor you'll find that the C/R is actually around 10.2-10.4
Porsches C/R numbers are always a little optimistic especially on the 964 and 993

What ignition are you running that has more to do with cr than efi or carburetors

Seems like 10.1 CR is the best best. 10.5 "might" be to much. Not worth the risk after a complete rebuild. From what Ive been told so far that JE pistons dont have the squish that the OE mahles have so they tend to work better for the higher compression but dont have the relief cuts to run a wilder carb happy cam like the DC43 - 108 suggested by John D. Im not sure how much this cam will affect the static C/R in the cylinder. Any pros have some background on this?