piston broke.

[Spanish Dave]

I have just removed the rods and pistons from my 65 f/b and found 2 top rings broken and five cracked pistons .. on the skirts ... one really bad one that goes up to the rings and you can see daylight through!! I was going to measure the bores for taper, but I assume that it will need reboring now, it is already +30 so it will have to be +40 or 60 next. What causes pistons to go that way .... overheating, lack of oil or just over-revving? Is it a common thing? It should be interesting getting the block rebored here in Spain as they don't do thou's, just metric ... so I may have to do an accurate measurement conversion

 

[rbohm]

usually detonation causes the piston problems you indicated. factory cast pistons were not the best quality. if the bores look good, then check them over for taper, and roundness. if you need an overbore, have them bore it with in .028" and hone it the rest of the way yourself. that way you can set the clearance yourself. or you can have them do it like you want it done. when you get new pistons, assuming you choose cast pistons, get trw pistons as they are better than the factory ones.