Rear Seal Adapter

The MOROSO Rear Seal Adapter (MOR38315) is a precision-engineered aluminum component designed to adapt 1-piece block rear main seals to 2-piece crankshaft configurations on small block Chevy engines from 1986 and later. This adapter solves a common engine building challenge: when transitioning from an older 1-piece block design to a 2-piece crank architecture, the seal housing geometry no longer aligns without an intermediate adapter. The MOROSO solution bridges this compatibility gap with a straightforward aluminum design that maintains OEM seal functionality while accommodating the newer crankshaft configuration.

Built from aluminum for weight reduction and corrosion resistance, the adapter integrates seamlessly into the pan rail of 1986 and later small block Chevy applications. The lightweight construction (1.35 lbs) keeps parasitic weight to a minimum, a consideration that matters in performance and restoration builds. The compact profile—6.75 x 1.75 x 6.85 inches—fits within standard engine compartment clearances without requiring additional fabrication or repositioning of ancillary components. Proper installation requires the correct pan gasket and fastener preparation, as the adapter creates the critical seal interface between block and crankshaft.

Engine builders, restoration specialists, and performance enthusiasts encounter this adapter when swapping internally balanced crankshafts into earlier small block Chevy blocks or when rebuilding engines with mixed-generation components. The 2-piece crank design offers superior dynamic balance at high RPM and simplifies certain machine work compared to 1-piece counterparts. This adapter is essential for those who prioritize mechanical compatibility and seal integrity over other workarounds. It's a direct-fit solution that requires no modification to the block, pan, or crank—install the adapter, torque the fasteners to specification, and proceed with assembly confidence.