ZIPPERS PERFORMANCE THUNDERSPORT CYLINDER HEADS HARLEY EVO

ZIPPERS PERFORMANCE THUNDERSPORT CYLINDER HEADS HARLEY EVO

SELECT LEVEL OF HEADWORK IN OPTIONS 

THESE ARE AN EXCHANGE ITEM 

STAGE 1-These heads receive our Stage I Performance Valve Job, 1.850” O.S. Valves, new guides and 7mm conical springs. The head gasket surface will be skim decked to assure a true/flat sealing surface. This is a high quality upgrade for a budget build! Combustion chambers are stock 78 to 83 cc.

STAGE 2-Special high velocity port design with 1.850/ 1.610 valves. Valves and
7mm conical springs. Designed for engines with factory or aftermarket flat top
pistons or dome pistons. The combustion chambers are 78 cc to 82 cc range as
cast.

STAGE 3-Owners of Evolution® powered Big Twins can increase their engine’s output with a set of our CNC-ported EV heads! The factory casting is CNC-machined to our proven high torque, high power port shapes and the valve sizes are increased to 1.900” intake and 1.630” exhaust. Ductile iron Step-Lock guides are fitted and topped off with high quality Viton® seals and a performance spring kit. The head gasket surface is decked for flatness before final assembly.