Rear Main Seal - Ford 351 (#85339)

The Rear Main Seal for Ford 351 (#85339) by Cometic Gaskets is engineered to eliminate oil leakage at the crankshaft's aft end—a critical failure point in high-mileage and modified 351 engines. Whether you're rebuilding a classic muscle car, restoring a performance truck, or refreshing a tired short-block, this seal prevents costly oil seepage that degrades engine bay cleanliness and can lead to catastrophic bearing wear if left unchecked. Cometic's precision manufacturing ensures a reliable, long-service replacement that outperforms OEM rubber compounds in durability and heat resistance.

This rear main seal is designed with advanced elastomer material that maintains its sealing integrity across the full operating temperature range of a 351 engine, from cold starts to sustained high-load driving. The seal's geometry is precisely matched to Ford 351 crankshaft journals, creating a positive, non-damaging contact that prevents bypass while resisting extrusion under peak crankcase pressures. Cometic's manufacturing tolerances and material selection eliminate the common cause of leakage seen in inferior aftermarket seals—premature hardening and loss of elasticity—making this component ideal for both street and track applications where reliability cannot be compromised.

Mechanics and engine builders standardize on Cometic gasket products for their proven track record in 351 Windsor and 351 Cleveland platforms. Installation requires engine removal or transmission drop-down access; proper crankshaft cleaning and seal driver usage ensure correct seating and long-term performance. This seal is essential for any 351 rebuild, stroker conversion, or oil-weeping repair—whether the engine runs stock displacement or carries boost, nitrous, or significant cubic-inch upgrades. Verify fitment with your specific 351 variant and confirm transmission adapter compatibility before ordering to ensure seamless installation.