It had higher (9.0:1) compression, a larger air cleaner intake, lower-restriction exhaust, a dual-outlet exhaust manifold, larger carburetor venturis, and a higher-lift camshaft.
It has a cast-iron block, aluminum cylinder head and uses a lateral camshaft to operate overhead valves, which also operated the fan belt on its other end.
The intake ports are then re-located between the intake and exhaust camshafts, just above the spark-plugs, pointing at an outward angle from the vertical.