2.8 Build

[abisel]

Rod bearings:

In this thread: Rod Bearing Controversy and the use of Clevite bearings over Glyco?

And what about main bearings? Are their issues with Glyco for main bearings? And the number 8 bearing, thrust bearing and intermediate shaft bearings?

[abisel]

BTT.

Any further comments on the use of Gylco for main bearings?

A few posts back I asked about intake valves. Any comments on preferred brand for the 2.8 10.5:1 engine.

Cheers,

[Walt Fricke]

Looking at the various experiences with bearings, it looks like the rod bearings are where the problems arise. The rest seem fine. In my 2.8SS case where the rod bearings had their Calico coating worn off after two sessions on a chassis dyno (total run time less than one hour), but the mains looked fine, the mains were hardly put to the test.

The 130 hour or so 2.8 I pulled apart to freshen up the bearings after the SS 2.8 blew up ended up with me regretting doing it, as rods and mains all looked like they were good for an unknown number of more hours. Those bearings were maybe six years old (but hadn't been run that many race seasons). So maybe it is a quality control thing, or a change in materials, for the rod bearings?

But it is Clevite for me from here on out.

I don't have enough experience to have valve brand favorites. However, what I'd like to know is how much larger a valve can you get in a 92mm cylindered motor? In my SS with 95mm to play with, I got 8mm stemmed 51.5s as used in the 993 RSR or something (though not sourced from Porsche - the guy who did the valve guides sourced valves and springs and retainers and I don't know from whom). But I don't know about the 92mm jobs - Porsche had to change the valve angle in the 2.8 RSR in order for the 49mm intakes to fit. Would a 48mm fit? Would you need to have the valve seat cutout in the head cut larger, and a larger OD valve seat installed? Or could you cut the stock ones larger?

[abisel]

Thanks Walt. What you said about bearings is what I have so far. Just verifying.

As for larger valves in the 2.8 heads, I don't think you can do it without enlarging the combustion chamber and then go with larger OD seats. But what would that do to the seating surfaces between cylinder and head? It would get smaller and more prone to blow out I would think. If you scroll down, I posted a picture of the 2.8 head and the seats are right on the edge of the combustion chamber.

I have read pros and cons on Interlake and TRW valves and then I found the SM valves from Germany. An old-school German mechanic that races his '68 2.0 believes the SM valves will be fine. I have the exhaust but need the intakes and finding the SM intakes seems to be an issue. I may have to source them from Germany. Should I get sodium filled intake valves or just go with the standard intake valves?

[Walt Fricke]

Ah - I had forgotten that you had real 2.8 heads. Perhaps envy did that. No need (and probably no possibility) of larger valves. You could adjust where the valves seat, though putting them where Porsche did couldn't be bad.

I was wondering about the possibilities of 2.7 and earlier heads using the 92mm jugs.