2.4 crank in 2.2S?

[hydra]

Hey all,
I've got a spare 2.4S crank/rod assembly, and seeing as I'm about to rebuild my 2.2S engine anyway, I figured why not stroke the engine out a little while I'm at it. My question is, is this pretty much a plug and play swap, or is it a little more involved than that? Where would compression end up at? Would I need to modify the MFI pump to allow for the increased airflow or would it still be within adjustment limits? Finally, for all you purists out there, would it in any way dilute the essence of the car (a REAL 2.2S) ?

[trak ratt]

Any outward change to an original S can lower its value in the purest eyes. The 2.4 crank will drop right in but you should carefully check the relative position of the piston wrist pin and of course do all the usual valve to piston, and deck height checks. Early none S 2.4 cranks were not the same high-grade steel as the Ss. Not a big issue unless you intend to spend a lot of time at maximum RPM. After adjustments to the MFI you will likely see about an 8 to 10% increase in power and torque (9% increase in capacity over the 180hp for the 2.2, or about a full point increase in compression over the 2.4S 190hp). I wouldn’t do it unless the engine really needed a rebuild. But it would make a nice upgrade to the 2.2 and would probably improve drivability some.

[jluetjen]

My question is, is this pretty much a plug and play swap, or is it a little more involved than that?

I think that "the devil will be in the details". Specifically...

1) You'll need to crack the case to replace the crank. Chances are once you've done that you'll find that the case will need to be R&R'd with an align bore as well as refacing, clean the squirters, oil by-pass mod, a little of this and a little of that.

2) Of course you'll need to R&R the rods by resizing them. While you're in there it most likely wouldn't hurt to have them polished or shot peened, and balanced.

3) I'm pretty sure that the head should flow fine as is. Chances are the pump will be fine to with a little adjusting.

4) I believe that your pistons are Biral, so they will need at least a re-hone if not slight bore to make the walls straight since the pistons run in iron sleeves.

I don't remember the 2.4S cranks being different like the 2.0/2.2 cranks were. But at my age, I may just not remember...

[BK911]

What I would do?

Find a 72/73 case to build on. They already have the case squirters and are stronger than your 70S case. Put your original case on a shelf. Even if you blow an engine, the original case is still intact. Use all your 2.2S components on the 2.4 case with the 2.4 crank and rods. BOOM, done.

edit: As far as the purists go:
Do whatever makes YOU happy. It's easy to de-stroke the engine. Well, it's not too difficult. Personally, I can't believe the purists don't shelve their original engines and try different combinations.

[NevenM]

What would I do

Build the engine back to stock (if anything at all), a 2.2S is a special car, any 'improvements' you make will only devalue it

HTH

Neven

[Alan.UK]

That’s a difficult one. Your S is a 1970 and therefore does not have piston squirters, so if you wanted to start upgrading your motor, it’s more than just a drop in a 2.4 crank affair, plus the MFI may need changing/altering.
I am rebuilding my 2.2S soon and I am going for the original spec as the car is pretty original, but if I also did not have another 911 with a little bit more street grunt it would be a hard decision what to do.

Good luck

Alan.UK

[hydra]

If the case wasn't going to be opened anyway I wouldn't even dream of doing this, but since I'm going to overhaul the engine anyway, I figured why not...

Regarding originality, I do have a 2.4S case handy, but I would very much like to keep the original 911/02 case in the car (which btw is 100% original) With that in mind, would a mod like that have any negative (or maybe even positive?) effect on the value of the car? I realize that the 70-71 2.2S is a gem and is highly prized by Porschisti so I'm not sure I want to mess with the car, but on the other hand its potentially a great mod... What do you guys think, would you do it?


PS Are all 2.4/2.7 cranks created equal? If not how do I tell the diff between them?

[hydra]

bump

[BK911]

Anything that you do that is not original will devalue the car. With that being said, I would still put the original case on a shelf. What happens if you spin a bearing or throw a rod? Now you've just lost thousands. How much is a 70S with a stroked 2.2S engine plus the original case in rebuildable condition worth? Personally, I'd pay more. Why even take the chance of damaging the original case? I'm just not a gambling man.

My 71E has the original case on a shelf.
My 73.5T has the original case on a shelf.
If I restore my 70S, the original case goes on a shelf.

Of course this is my opinion. I am curious what others think.