Put a thin layer of clay into the valve reliefs of one piston. Install a single head with and old head gasket, torque it down, then install one intake and one exhaust lifter, pushrod, and rocker, on the cylinder with the clay. Turn the engine over two revolutions, then disassemble it again. Measure the thickness of the clay at the deepest point of the valve impression into the clay - this will be the minimum piston-to-valve clearance.
.080 is the minimum I'd feel safe with, although I've run as little as .060 before and not had problems. If you see silver through the clay, that means the valve is actually hitting the piston, and you need to machine the valve reliefs in the piston a little bit deeper to get adequate clearance.
~Scotch~
|