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Originally Posted by Jake Raby
There is no other bearing opposite the failure prone IMS bearing.
There is no bearing insert in the case, the bearing just rides against a machined portion of the case and is lubricated hydrostatically... The cams ride in the heads without bearing inserts as well.. Much like a 36HP VW engine or a 356 engine- No cam bearing inserts.
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Well, that's a surprise! Now I am left wondering why Porsche designed the engine with a pressure lubricated bearing surface at one end of the IMS, but a sealed bearing at the other end. I know that the use of the aluminum case and head surface as bearing area is very common -- most overhead cam cylinder heads are built this way -- but the use of a sealed bearing inside an engine is highly unusual. I have seen sealed bearings used successfully inside transmissions, but in that application the bearing does not have to cope with fuel and water laden engine oil attacking the seals.