The cylinder heads are Ford's highly efficient "Z" heads. They are already popular with hot rodders and should work well here. They feature angled plugs, 63cc CNC-cut combustion chambers, and relatively small ports that still flow well for good throttle response on the racetrack. Valves are steel, and the standard size for stock car racing is 2.020 inches for the intake and 1.600 for the exhaust. Since no modifications are allowed to sealed motors, the CNC-cut chambers are a nice touch. They should help ensure consistent power from one engine to the next.