Simply "no interference" won't be sufficient- - - -you'll need a bit of safe zone at the minimum clearance point. I like to use .060" as a minimum. Start a few degrees away from the expected minimum clearance point with a weak spring on the valve, and push the valve down with a lever until it contacts the piston. Use a dial indicator on the spring retainer to measure the travel. Turn the crankshaft 5 degrees and measure again. "Rinse and repeat!" It's not uncommon for the intake valve to outrun the piston near the top of the stroke and the closest contact possibility to happen after TDC if the cam has a pretty radical rate of lift. It might be necessary to do a little flycutting on the pistons if a thicker head gasket can't create enough clearance, or even run the cam a few degrees retarded. Advancing a cam increases low end torque- - - -retarding it helps top end HP. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
