[Walt Fricke]

Well, the 964 valve covers have holes in them in the same places the earlier covers do, just smaller diameter. Not much of a problem, and I've seen earlier motors with these covers (and their nice rubber O-ring type gaskets). (Me: whadayuhdoin with a 964 engine in this class? Huh? The valve covers! Oh, we just put those on - the engine is based on a sandcast case and is a 2.8. And it was.)

My suspicion is that since Porsche doesn't change things like stud spacing often (and then only to accomodate things like larger spigots), and the cylinder center to center distance holds constant, the studs holding the cam carrier to the heads are in the same place and are the same size because there would be no particular reason to move them around.

As to the chain housing, Porsche added one stud and some bushing dowels at the same time or about the time they went from the 6 stud to the 11 stud exhaust valve cover. So I'd guess that the 964 and newer chain housings might bolt on.

I'm less sure how much trouble it would be to convert to the spring loaded chain ramp system with or without the internal oil line (and this might be the only reason to want to use these chain housings).

What I really might care about is the revised rocker shaft system where the shaft is just bolted at each end to the cam carrier. That sure would be nice for top end work and for removing a source of grime producing oil seeps. Did that come with the 993s? But would cam carrier compatibility with the pre-964 heads still prevail?

Walt Fricke