I think the 7R case is nice to start with, if you can find a good one (lots of CA emission ones got very hot). My own personal experience is that the 3R cases (especially the T) were not stressed nearly as much and will last just as long if not longer than the 7R case. My own personal experience is with a 3R case that was rebuilt to 2.7RS MFI spec 40K miles ago and has not had any problems. The case was time-certed and divalar studs were used (this was in 1990).

MFI is the way to go. A short stoke 2.5 will not have the torque or power of the 2.7RS spec engine. I would only go the 2.5 route if restricted by class rules. The 2.7RS MFI engine is best driven in all conditions to realize just how great this engine was for its day - and still is. It is the perfect Porsche flat six engine in my opinion - especially in a slightly stiffened early 911 - the balance between motor and chassis is magical.

machine work
 

As far as access to a vertical mill, I'm looking at one right now. I'm a engineer at a small manufacuring company and before that, I worked as a machinist here for 8 or so years. I have no problem doing the machine work myself, I just don't have access to the technical drawings/specs I'm sure I'll need to feel comfortable. Installing case savers and spigoting the cylinder bores seems straightforward to me, but I'll know more after I split the cases.
BTW, I'm in Northern California.

Jim

I am asking. I am too in the process of rebuiling my 1970 2.2 engine. Lets say that id like to keep the early engine, like their rawness. I have a small budget but have access to low-cost labor. Already have E-pistons/cylinders and S-cams into my T-case w/counter-balanced crank. So here are my two options :

1) Use 2.4 crank and rods, w/2.2E pistons and 2.2S cams.
What will it give in terms of HP?

2) Short-stroke 2.5, again w/2.2E pistons and 2.2S cams
What will it give in terms of HP?

Your choice BETWEEN these two please.

Many thanks.

PS i KNOW a 3.0L would be preferable.....

Farleyd, use the 2.4 crank and rods, I think in the past on here everybody agrees on 180+, maybe 190 at the crank, stock 2.4 E is 185 SAE and 165 DIN. If I had that stuff and was on a budget I'd say go for It will be a nice engine when your done. The important thing is to NOT skimp on the details, check the case, add case savers, oil bypass mod etc. OH yea....MFI nuff said..


BTW, I might start a fight here, but.... I suspect that a properly tuned 2.4S or 2.7RS spec engine in an early car would have the upper hand against a "stock" 3.0 transplanted in the same car. The money would probably be about the same depending on the details. Of course you could later hotrod/rebuild the 3.0 so..... take from these comments what you will. If you build the smaller engine, you can still have the numbers matching equipment that your car came with.

great thread!

need to bump to archive in my email

Great thread, guys. I have a pretty fresh (30,000 miles) 2.4 T motor right now. I have been playing with all the ideas presented here, with no real first hand knowledge on any of these possible combinations. This thread has been most helpful in planning the future of my 2.4. It has a lot of good years left in it right now, but some day, I'll be in the same boat contemplating what to do next.

Wow this thread was a blast from the past.
Now I have this CIS 2.7S mag case motor from my racecar on my engine stand and am about to start reassembling it. The 2.7S CIS does not have the spirit of early MFI powerplant or the joys of high revs. Just a steenkin' mag case! What a dramatic step back these motors must have been to the factory engineers who knew what MFI 2.7/2.4/2.2/2.0 could do... I think my 2.4S MFI motor is one of the sweetest engines I ever driven (and thirstiest). This is from a guy whose daily driver is a 3.0 SC now.

I vote you find a 7R case and do what is needed to bring it up to date...(and there is quite a bit) you will have a fast light pwr plant with less weight behind the wheels.

Guys,

sorry for the intrusion, very nice thread.
I have a little problem... My mech says I have to replace my '72 2.4 E cylinders because they are too worned. Is it any way to rigrind / resurface / or other to bring my old cylinders to a new life ?

Thank you very much for any suggestion !

Bye.
Steve

No intrusion at all. That's what this site is for.

in re: Your cylinders.

Yes,

You can bore them out to 85mm or possibly larger and buy some custom pistons, like JE's. You can also raise the compression ratio with the custom pistons for an even better performance increase as well.

Not sure whether you can bore out Biral cylinders which is what 2.4E were originally, I believe not. You might be able to get them refurished by EBS in Reno. Give Jon @EBS a call. HTH

Would it be more cost effective to source a 7R case and 2.7 RS pistons and cylinders, basically build the long block from scratch and reuse the T MFI, than rebuild the existing 2.4T long block?

Only if the 7R case in question doesn't need a lot of machine work to be usable which isn't likely. Possible but not likely.

Most 7R cases need substantial machine work before they can be used. This can costupwards close to $1000 depending on how much needs to be done.

2.4T cases on the other hand seem to fare better atleast in my limited experience.

If you can find a 7R case that can be verified as ready to build at a reasonable price then your ahead of the game.

Basically cutting spigots on an otherwise healthy case isn't that expensive.

A 2.4T 7R case can be a very nice foundation for starting a mag case rebuild.
they can be somewhat difficult to find. They were used in late 73' on 2.4T CIS motors.

Just to verify, if I'm dropping a bone stock 2.2E motor and want it rebuilt to a high compression 2.4, all I need is a 2.4 crank and rods?

Any other things I should consider "while I'm in there?" I want to keep the existing case since I believe this motor to be original to the car.

The 3R is a mag case, no?