Building a 2.7RS Engine
 

I'm getting ready start building a 2.7RS Spec engine and I have a couple questions:

1. Is it better to start with a 2.4T with MFI or a 2.7 CIS Engine?

2. If I start with a 2.4T engine is it possible to have the cam shafts welded and reground to "early S" specifications?

3. Would you recommend using Mahle 2.7RS P&Cs or the JE high compression RS P&Cs?

Thanks

Depends, conventional wisdom says that the 2.7 cis cases have seen more heat and may be more distorted or stressed than a 2.4. That said a 2.4t MFI already has all the fi parts that you will need. They just need modification. either will work it just depends on the individual engines that you are dealing w/


yes, speak w/ the cam people about specifics

Mahle, I have spoken w/ quite a few builders that used to recommend JE but no longer do. There may be unique circumstances where JE is a better choice, such as a pure race engine that will be regularly taken apart inspected and remanufactured, but for most of us long term durability is more desireable than saving a few bucks on a one time rebuild.

Bill, do you happen to know the best place to get a set of Mahle high compression p/c. for a 2.7? I'm looking to start w/ 9.5:1 maybe. Is there any other place than Andial? Thanks.

You don't really have "all the fi parts you need". The velocity stacks are too small in diameter and cannot be bored out because they are thin plastic. I also think the throttle bodies are the wrong size but that might not be true. The MFI pump should have it's space cam changed. You might be able to find some Magnesium velocity stacks from a 2.2 engine. These can be bored out to the required size. Your throttle bodies can be overhauled/changed by Eurometrix.

Other considerations are 2.4 T may not have a 7r case. 2.7 CIS heads will not have the right openings for the MFI injectors.

The previous owner converted the 1972 911T I have into a 2.7 RS spec. He used the old case (5r) and did the things I talked about to the MFI. It cost him over 10,000 dollars in 1991. Worth every penny though.

-Andy

Sorry Bill, I didn't notice the caveat you put in about needing to modify the fi parts.

One other consideration for the MFI is that if you use the magnesium stacks you'll need to change the way the cold start enrichment works. Mine has small hoses running along the top of the air cleaner to little plastic injectors that sit over the stacks.

-Andy

There's a lot of info about this sort of thing on this site

Here's one
http://forums.pelicanparts.com/showthread.php?s=&threadid=117171&highlight=mfi+ch art+stack+throttle+bodies

Go to the Mahle website and check price and availability with all their distributors.

The Porsche pistons catalog is downloadable in a PDF file from this page in the Mahle Motorsports section.

HTH,
TT

Thanks for all the great information. I'm starting to collect all the parts so this is very helpful.

I contacted a distributor of Mahle p/c's and they said only there's only 2 distributor's in N. America that sell the Porsche pistons: SSF and Andial. Contacted SSF and they said they won't sell to individuals. Oh well.