Grandpa#3

I read some where that the 92 968 had weak pistons or rods. I was wondering if anyone has information on this subject? Any help would be much appreciated.

Cheers,
Larry

JDS968

It's the rods. The big ends don't have enough metal in them where they bolt together with the caps.

FRporscheman

I thought that was all 968 rods though.

I do remember reading somewhere that the 1992 cars (and maybe only the earliest ones at that) had cast instead of forged, but I can't remember if it was pistons or rods. I want to say rods.

JDS968

Not so far as I know.

EDIT: From the workshop manual, page 13-35:

Reinforced connecting rods

Adopted for production from Oct. 1, 1993, as of the following engine numbers:

42 R 00 598 (engine type M44/43)
42 R 50 621 (engine type M44/44)

Vilhuer

Porsche says early ...1R casting number rods should be always replaced with late ...2R casting number rods when nuts are opened. Big end neck is 17mm wide instead of 10mm. Weight is still same.

Dave in Chicago

Please see below:

FRporscheman

Ah yes, I remember now. Good info, thanks guys.

But there was also something about cast vs forged regarding one of the internal engine parts for the early 968s, wasn't there? Or was this all?

JDS968

If so, I've never heard it before.

Grandpa#3

Thank you all for the information on the rods. Now I wonder how many engines were trashed because of these poor rods?? I was thinking about buying a 92 968 Cab, now I don't know if I will or not.

Cheers,
Larry

dougs968

Hi guys, there is a pretty good review in volume 9 Up-Fixin der Porsche. And I quote: A close look at the technological details of Porsche's beefy four-cylinder powerplant. The 968 Engine: Big Bore Makes Big Power.
By Herbert Ampferer
Chief of Engine Development
Porsche AG at Weissach

In the article he says they looked at cast and forged rods. They went to the "130 gram lighter, but somewhat more costly forged rod."
Volumes 9,10 and 11 are/were free for the asking to PCA members.
Doug.

FRporscheman

I've never heard of a problem with the old rods, I think the old ones are fine for normal use (i.e. no turbocharging or hard track driving).

Vilhuer

968 and 928 GTS rods are somewhat different compared to earlier rods used in same engine family. AFAIK they are forged but not same way as earlier forged rods were which were used in early 951 and same period 928 engines. Those are really strong ones while 968 setup is actually weaker than practically any other rod used in earlier 944 and 928. Both inline-4 and V8 used same basic measurements. In 928 rods 2mm was removed from one side at big end to allow two rods to be closer to each other on same crack neck.

I believe these later rods were compressed together from small metal pieces under very high pressure. This allowed them to be lighter than earlier options. It was desirable to minimize rotating weight on these long stroke engines as crank counterweights could be kept smaller. But they are weak no matter what actual production method was. Some can take turbo or SC use but knocks will kill them much easier than earlier designs, even in NA engine. Late '94-95 MY ...2R casting number version is somewhat better but I would not use them in anything but NA engines either. There are much better aftermarket options available.