The stock multi-groove valves are not to be used for high rpm use. They grip the valve stem loosely(to allow the valve to rotate for even stem wear) and have been known to cause "dropped valves". I have experienced this on an engine that was never pushed past 5500 rpm. I dropped a valve, put a hole in the top of the piston and cracked the block. This was while cruising along at a leisurely pace and not while racing. Although 2 years of hard use and street/strip duty played a part. The stock exhaust valves are of a 2 piece design and have been known to seperate under high spring pressures. I am presently rebuilding a cleveland for my 72 mach 1 and I am using stainless valves with single grooves and a completely new valvetrain. I feel that I have spent too much money on machine work to take a chance with the stock multi-groove valves. The stainless single groove valves can be purchased for about $200 from any mail order supplier or your local machine shop. Good luck, Tom
|