[Ron61]

Toby,

When you stroked the engine out, did you just increase the rod length or have it bored a little more? You know the formula: Cubic inches= # of cylinders X .7854 X Bore X Bore X Stroke. And how did the other pistons and rods look? If all other cylinders are ok, you could have had a faulty rod. From what you describe, it sounds as if for some reason the #3 piston hit the valve and spark plug. If all the clearances are good, it could also possibly have been a valve sticking open for some reason and then the piston hit it and the rest was history. Sorry I can't tell you more, but I am sure some of the guys here will be able to.

Ron