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From GM -  602 Spec - Cylinder Head: Cast Iron Valve Diameter (Intake/Exhaust): 1.94”/1.50”

Crankshaft: Nodular iron,  

Camshaft: Hydraulic flat tappet

Rocker Arm Ratio: 1.5:1 - Stamped Steel 

602 Link -602 Specs

604 Spec - Cylinder Head: Cast Aluminum, Valve Diameter (Intake/Exhaust): 2.00”/1.55”

Crankshaft: Forged Steel, 

Camshaft: Hydraulic Roller Tappet

Rocker Arm Ratio: 1.5:1 - Aluminum Roller

604 Link - 604 spec