501 Series Performance Head W/ seats and guides 42 Intake 37.5 Exhaust

Made from an AA 501 Series Casting, It is set up to build the performance Head of your needs. It Comes with Seats 42x37.5, Guides,with a 12mm plug hole.

The 501 Series Castings come STD with: Increasedmaterialat the intakesurfacegivingyou theabilityto make much bigger ports. Amodernized Combustionchamber, for increased head flow & performance. AsecondFull Fin, soyoucanFlycutyourheads deeper to achieve almost any desired Head CC volume needed. Blocked off rocker stud bosses, to eliminate the O-ring and stoppossibleoil leaks. Long reach 3/4 Inch SparkPlugs, toreduce the chance of cracking betweenthe Valve seat and Plug.

Casting: AA 501

Valve Size: 42x37.5

Head CC: 55cc

Head Bore: 85.5

Plug Size: 12mm (ReplacementNGK Number is D8EA)