drnick

swaybar, do you have the wet sleeved engine in place and is this then a spare engine? i guess it depends on what you want to achieve with the engine vs your financial resource! how many miles were on the engine and who rebuilt it? interesting combination of parts.. do you think the pistons are GTS? they have shorter skirts and are physicaly smaller than the others. i would have thought the wrist pin offset would preclude there use without the matching GTS crank ie the compression ratio would be stupidly low... check my pics on page two of this thread for GTS piston pics.

heinrich

I'd trade my full set of 8 968 pistons with 928 rods for a good set of GTS rods and pistons

heinrich

Swaybar I have good S4 rods and pistons I'd trade you for your rods and pistons.

adrian928se

GTS Piston pic or Swaybar. Would be interested to see pics of pistons that came out of your GT. Sound like a batch Mahle did for the 928.

PS if anyone has a good set of 8 968 pistons and rods they want to sell, I'd be interested

Adrian

SwayBar

It is a spare, but it is going into another car, street-only.

The pistons in the GT bores do not look like yours nor Adrian's as there is a tab on the skirt like an S4 has. However, there are no oil-ring holes in the pistons; I thought GTS pistons were the only ones which did not have the oil-ring holes. Has anyone ever seen a piston as I described?

Finally, the casting number on my block ends with 1R, just like the rods.

Thanks for the pic Adrian.

ROG100

Erkka and the rest of you engine boffins,
I have thought about Supercharging my GTS in the future and this thread has me rethinking that decision.
My car is a later 93 car and the VIN ends with 820119.
Should I or not? Does my car have the later rods?
Thanks,
Roger

rayqblue94

Roger,
Porsche Tech. Info -20/12/93 -81033 introduction 14th SEPT. 1993 .
New type con rods [2R] ( 17mm wide instead if 10mm wide[1R])for M28/49 engine No's from 85 R 00533 and M28/50 engine No's from 81 R 50597.
Hope the lottery is kind to you.
Cheers
Ray

GregBBRD

As I think I mentioned: the 968 rods definately bend/eventually break with 1 bar of boost. I've got samples. Don't take it personally, but I think you guys playing with superchargers on a GTS engine are playing with a hand grenade. If you use the early rods....the pin fits very loose in the grenade, me thinks.

drnick

greg, i agree with you in that there is no question the later style rods are stronger. but equaly so is the fact that there are a good number of engines out there with this type of rod, naturaly aspirated, running without problems. the quesion of boost... no doubt a stronger rod is better. but if the boost is limited to 7-8 psi perhaps it will be ok. im not planning any more boost than this, my goal is 500 bhp at the crank.

SwayBar

I found the Technical Bulletin number 9401 regarding "Reinforced Connecting Rods". On page 2 under 'Repair Information (cont.):

"NOTE: In the beginning of production, reinforced connecting rods were installed with the old casting number ending "1R"; therefore, before replacement, always measure the width of the reinforcement rib "A".

New version (1) = casting #944 103 111 2R = dimension A is approximately 17.0mm

Old version (2) = casting #944 103 111 1R = dimension A is approximately 10.0mm

Wide connecting rod shank = new version = can be reused
Small connecting rod shank = old version = replace

All connecting rods with the casting number ending in "2R" (arrow) can be reused if no other damage is present."

Armed with this new knowledge, I went out and looked at my "1R" rods, and lo and behold, they are, according to the TSB, "2R" rods; YAHOO!

So now I must decide if whether I want to remove the pistons to drill oil-return holes in the pistons behind the oil ring.

Alright, here's the upporting screenshot I should have just posted in the first place and should clear up some confusion on the GTS rods:

Vilhuer

R = '94 MY. First engine number was very likely 501 like in several previous years. This means even early '94 MY engines use 1R rods.

Those change points give also insight on ratio between automatic and manual gearbox cars. (533-500)/(50597-50500) = 1/3 manuals.

968 might not have problems but they got new rods too as both models used same raw casting. 2R is clearly stronger but both are weak compared to best forget rods used in 951.

Besides no oil return holes GTS pistons are easy to identify from extra groove on side between rings. I haven't seen any other pistons with similar setup.

tomboyea123

Any Idea as to what date porsche went to the later style con rods for the gts motor and when porsche went to the good rods for the gt motor?I have a spare 89 gt engine and a murph kit on my 93 gts motor. Thanks

Vilhuer

September 14th 1993.

I would say never in GT or same period S4. Never because I think Porsche might have used whatever rods they had on hand when they build last '91 GT and S4 engines. They knew they needed to use lighter GTS/968 rod casting in GTS and thus might have used whatever they had few extras for late GT engines. This could mean some late '91 MY engines have good rods and some don't. As always this is impossible to know as AFAIK Porsche did not give any engine number when they did part changes to those engines.

I think no matter what rods are used crank should be balanced if rods are not from that same engine. Thus any 944/951/968 rod can be easily made to fit into any 928 engine by competent shop. Some aftermarket companies like Pauter make rods for 951. These or other aftermarket stuff is way to go in 928 too if engine is boosted.

'93 MY GTS will definitelly have early style weak rods unless engine has been open some time in past.

drnick

how many miles do you have on the boosted 93 GTS engine and what psi?

tomboyea123

The engine has about 62000 miles with about 1000 being supercharged.I am running about 6-7 lbs of intercooled boost.