I need advice please!

M491Cabriolet · 09-02-2008, 03:10 PM

OK guys... I have asked this question several times, but the typical answers have been something like, "drive one of each and decide for yourself!"

So, as a premise, I don't know anyone with Porsche longhood cars around me and have access only to my own car.

The premise and questions are... I have a 2.4 911T MFI engine I am rebuilding. I have a 911E MFI intake setup and new E cams. I have a set of 2.4 911S pistons and cylinders and a set of 2.2 911E pistons and cylinders.

I am at the point in my rebuild process that I have to decide which P/C set to use and I REALLY need some good advice from a good hearted soul with experience and wisdom. If I go with the E P/C set, my compression will be higher than the S P/C set. But I'm wondering about a few things.

First, for a fast street car, will the higher compression (9.6:1?) 2.2 911E pistons with a long stroke make a noticeable difference in the feel I get from the car?

Second, will the compression ratio from the 2.2 911E pistons mean having to use only the highest grade of gasoline?

Third, is the 2.4 911S setup with its stck 8.5:1 compression ratio inferior to the 2.2 911E setup on a long-stroke crank?

Which would YOU choose?

PLEEEEASE help!!! Thanks.

911st · 09-09-2008, 01:47 PM

I think the S pistons are forged and the T are cast. Not sure about the E's if it matters.

I like your choice of an E cam. The E's seemed to test as a faster car in there day.

I had a factory 2.4S and during the build we decked the case. After setting the deck height for about a .040" head to piston clearance if I recall, I think the compression measured about 9.2/1.

I would not want to run 8.5/1. Would like something close to 9.5/1 but I am surely not an expert.

An aggressive cam needs compression to work its best.

Thus, if it were me I would use the 2.2E p&c for 9.6/1 but make sure there is no clearance issue and would still check w an expert. I would also test fit one w the head and pour a measured amount of ATF into the spart plug hole w piston at TDC to verify the CR.