Originally Posted by QUICKVIII

That is classic piston slap noise. Remember guys when the engine is cold the piston is loose in the bore. As it warms up the noise goes away. Thats the piston heating up and the skirt expanding and tightening up the piston to wall clearence. NO lifters in the engine... No rod knock because as the engine warms the oil thins, this would increase the noise if it were a rod. Also if you were having a rod problem it would sound like a double knock, pulling the plug wires one at a time till the noise went away would help you pin down which rod was bad. No main bearings will cause a problem like that. if the mains were worn you would lose oil pressure and would be having a whole lot more noise than that. The engine will run for a very long time still.. Just remember it is getting old, it's a little tired. Be easy on it and it will last. Hammer it and it won't! Hope this helps. Dave Brauning...