Rear Main Seal Ford 351

The Rear Main Seal for Ford 351 is a critical engine component designed to prevent oil leakage at the crankshaft's rearmost bearing surface. This seal sits between the engine block and transmission bell housing, containing pressurized oil that lubricates internal engine components. Whether you're performing a full engine rebuild, addressing an existing oil leak, or restoring a classic Ford muscle car powered by the legendary 351 small block, this rear main seal for sale is an essential wear item that demands OEM-quality replacement to avoid catastrophic oil loss and engine damage.

This rear main seal specification (MPN SM85339) is engineered to withstand the demanding conditions of the Ford 351 engine architecture, where crankshaft rotation and combustion pressures create constant stress on sealing surfaces. The seal's elastomeric construction provides superior flexibility compared to older cork designs, maintaining a consistent barrier against oil escape across a wide operating temperature range. Precision manufacturing ensures a perfect fit within the engine's seal cavity, reducing installation friction and minimizing the risk of premature failure—a critical consideration when reassembling an engine block after machine work or transmission service.

Mechanics and enthusiasts restoring Ford 351–equipped vehicles—from performance street cars to vintage trucks—rely on this seal during transmission removal, engine rebuilds, or when addressing the telltale oil staining at the engine-to-bell-housing interface. Proper installation requires careful alignment with the crankshaft journal and application of the correct sealant to the block parting surfaces; many builders recommend replacing this seal whenever the transmission is separated from the engine, as doing so prevents future oil contamination of the torque converter and clutch assembly. The compact 4.55 x 1.05 x 4.8 inch dimensions and 0.2 lb weight reflect the seal's precision engineering for direct bolt-on compatibility with Ford 351 engines across multiple model years and platform applications.