The Edelbrock Performer RPM Aluminum Cylinder Heads feature threaded inserts in the rocker studs and exhaust manifold bolt holes for superior strength and durability. These cylinder heads offer dyno-proven increases in horsepower, throttle response, and torque throughout the RPM range. These heads have outstanding features that include phosphor-bronze valve guides, interlocking ductile iron valve seats and premium one-piece, stainless steel, high-flow 2. 02" and 1. 60" intake and exhaust valves. This head features a 63cc combustion chamber along with a 171cc intake port. Heat treated, machined steel retainers and valve locks along with heavy duty valve springs are good for 0 . 575"-lift cams. This powerful head uses the stock location for intake and exhaust bolt holes and flanges spark plugs and valve cover rails for compatibility with aftermarket parts.