[Walt Fricke]

Expert or no, someone is always adding to the stock of knowledge. Bent or cracked rockers I have never seen. Mine have all just broken - they are castings. Once broke all 12 in one go (aluminum IS gear shed its teeth). But if Jim has seen them, they were real. I once found I had cracked a forged chain idler holder, which explained why it was up so close to the top of the chain housing, but no other symptoms.

But it is vibration that is the immediate issue, not increased valve lash (noise, usually, and not just when reved). The #6 valve (exhaust?) may well be bent, but I don't associate that with vibration. I bent all 6 of those once, and drove for a year or so before pulling the heads when a shop said the car felt down on power. No vibrations.

I am not up on the early flywheel clutches. When I have broken the drive straps on my later ones the problems were in clutch disengagement, but since you have things apart you should be able to check yours, as the pressure plate is part of the engine's balance. A missed shift does put a lot of "backward" pressure on the pressure plate - way more than in normal driving.

Walt Fricke