[Walt Fricke]

Gene - I think you may be in for an engine drop. That, plus removal of the chain boxes and oil cooler, will give you some access to the ends of the rockers. If you are lucky, the #3, 4, and 6 will all have their big hex ends pointing outward, and you can go in with a small die grinder and grind off the protruding bolt ends. At least enough so you can get the hex to hold.

If a rocker binds when the bolt is tightened, most likely the shaft is mispositioned, and the slot is so far in that it is into the rocker itself.

One possibility here has to do with shaft length. The earliest shafts were shorter than later versions (it was the shorter shafts which sent a generation of DIY Porsche owners futzing around with a feeler gauge to get shafts properly positioned, while only these early short ones benefited from that). So I am pretty sure the early shafts had shorter hardware. Thus, if longer bolts are used on shorter shafts, the threaded end could be expected to protrude? If this is the case, maybe your shafts are OK. And the bores, too.

I can't imagine this bolt stretching far enough to do this - it would break first.

I also can't imagine that these were tightened so much that the cup pieces expanded the ends of the shafts (and thus the bores) so much that proper length boltss did this.

But who knows?

What if you can't get at things to grind the bolt ends? Or can't grind without ruining the hex? A drastic measure would be to try to tack weld a nut onto the hex cup. Or to drill a small hole between the cap and the housing, and then screw a sheet metal screw in, the notion being that if you can stop the rotation of the cap, you can unscrew the bolt. Will ruin the housing, of course.

I've not heard of anyone bushing the housing bores, but it sounds like something which could be done. It may well be cheaper to pick up a used housing (or two).

No doubt you have tried to get penetrating oil to penetrate the big hex/bolt joint?

This is a wierd one. Glad it isn't mine.