Vilhuer

Yes. Even better if you replace pistons with lower CR modified early S4 pistons and custom connecting rods.

drnick

this is not fair... not at all, not if the rods in my engine are going to either bend or break. it would make more sense to simply use a GT or S4 engine to boost if this is the case. but how much of a reality is this, how much of a problem has this actualy been? how many early GTS engines are still running strong, what was the actual cause of the weakness?

Charley B

There was a thread here recently with photos of the early and later GTS rods. There is an obvious difference in size. There is some anecdotal history of the early rods bending but little detail about the cause of their demise. That is, actual history of what was going on in the engine at the time of the damage. Greg Brown probably has as much experience with this as anyone, tho I don't know how much that is.

Charley B

I'm also curious if the S4 rods are different than the early GTS rods.

Vilhuer

GTS and 968 was going to be taken out from production and numbers made were very small in poroduction cars standards yet Porsche saw need to make change for these rods. AFAIK problems happened in quite small miles if they ever happened. Still, these rods are probably weakest of all stock designs used in 928 and four cylinder cars.

Before going for early 944 Turbo rod hunt I would check what stuff you have in now. First check is engine MY and next if it has later parts in it.

Vilhuer

Yes, totally different.

All S4 rods are not equal either. IIRR '87 use 944 Turbo rods while later S4 and GT have weaker parts.

Early 944 Turbo rods are even stronger and they can be modified to fit to all 928 engines.

drnick

here are pics of the rods in my engine. the engine serial no is: M28/50 81N 50505

slate blue

You U.K guys should now via your racing website somebody posted pics of a failed GTS rod. Made a very big mess. Nick please becareful, I don't want to hear you lost a motor over this. Also somebody may have changed them already, if you do decide to change them, great time to install the scraper system. I just ordered my second set for another project engine.

Greg

slate blue

I just saw your rods Nick, they look the early type, can't be totally sure because of the angle, Im sure that Greg B could tell though, the part that breaks is near the big end, it is much narrower on the early style rod than the late type, post your request on 928 racing for a pic, the workshop manual may show what the new rods look like.

Greg

Charley B

Those look like the early rods. A better picture would be standing on end with a side view.

Vilhuer

Agreed, those look early rod. Also piston rings and pistons are different between '92 which you have and '93-95 MY. You have worst of the three possible combination for boosting. I would try to find early S4, 944 Turbo or possibly S3 rods if you want to use those GTS pistons.

slate blue

Also if you use the S4 rods get ready to fork out some pretty big bucks for mallory.

Greg

adrian928se

Greg the pics I posted of the damaged (early) rods on the 928racing group, were from a 2/6 failure. I do have another set from a GTS auto that suffered a cracked bore and had slightly bent rods on some cylinders aswell as Thrust bearing failure.
I think Nick would be OK if he doesn't supercharge his car, as plenty of early GTS manual engines still around with the earlier rods. As for SC a GTS engine, personally I wouldn't do it unless boost was low, or later rods and much lower compression on the engine. (Thats why a went down the 5litre route in my SC GT).

Adrian

Fastest928

The only bent rods I have seen are due to engine failures from cracked bores..water is incompressible last time i checked. Although I have seen another engine with 8 perfectly bent rods, each one the exact same as the other one...and with perfect alignment of big and small ends. Never figured that one out completely.

I have dis assembled quite a few GTS engines and have about 3-4 sets of early rods and all are fine.

Still have yet to meet a 968 person who had a rod failure.

These rods are some of the finest rods manufactured, made by prankl I believe, and appear to bend rather than "break", a preferred failure mode in my book.

The only modification is at the base...it will improve the strength.

slate blue

By Marc@DevekThat would be Pankl, I think that is what you meant, makers of the Ferrari F1 connecting rod. Anyway I might be able to buy a couple of sets of 968 rods and have them machined down?

Greg