FACTORY IRON HEADS CARB ENGINES
Factory stud-mounted Ford Windsor cast-iron cylinder heads feature three main rocker configurations:
3/8" straight studs with slotted pushrod holes,
3/8" straight studs with round pushrod holes,
3/8" × 5/16" stepped positive-stop studs.
The Slotted pushrod holes guide the pushrods and maintain rocker alignment, while round-hole versions rely on factory rail-type rockers for guidance at the valve tip.
The stepped-stud version uses a smaller 5/16" threaded top and a shoulder that fixes the factory rocker setting.