S&S Cycle Crankcases — Harley-Davidson Softail Heritage Classic, Softail Fat Boy, Softail (1983-2026)

S&S Cycle MK-Series B crankcases for Harley-Davidson Softail models, engineered to support big-displacement builds up to 136 cubic inches. Features improved oil scavenging and large-volume sump design that fits in a stock Softail frame without modification.

Features

• Supports 136" cylinder kits and stroker cranks
• Improved oil scavenging compared to stock cases
• Large-volume sump design
• Fits stock Softail frame without frame modification

Specifications

• Brand: S&S Cycle
• Manufacturer Part #: 310-1326
• Category: Engine Components / Crankshafts
• Weight: 49.2 lb

Fitment

Fits Harley-Davidson Softail models. Verify your specific year and model with S&S Cycle before ordering to confirm compatibility with your build.

Frequently Asked Questions

What's the maximum displacement these cases support?

Designed to work with S&S 136" cylinder kits and 4 5/8" stroker cranks as part of a complete big-bore build.

Do I need to modify my frame to fit these crankcases?

No — these cases are engineered to fit in a stock Softail frame without frame modification.

Can I use these with a stock crank and cylinders?

These are built for high-displacement builds. Consult S&S Cycle tech support to confirm compatibility with your specific engine configuration.

What's included in the box?

Just the crankcases. You'll need to source a compatible crankshaft, cylinders, and gasket kit separately.