S&S M8 132 / 136 Big Bore Kit

When you're ready to go bigger without cutting the cases, this is the kit.

Collection of motorcycle engine parts including cylinder heads, pistons, gaskets, camshaft, piston rings, and other components on a black background.

The 132 / 136 Big Bore Kit is built around S&S 4.320" bore cylinders with ductile iron liners, an updated fin profile, and a texture black or black granite finish with machined highlights. Stock bolt pattern means no case mods and no machine work. It's a true bolt-on.

Two displacement options from the same cylinders: pair them with a 4.500" stroke crank for 132 cubic inches, or step up to 4.625" for 136. 0.0cc dome pistons keep the compression math straightforward, and the high-compression setup delivers serious power when matched with the right heads and cam.

These kits pair with our Ward CNC ported heads and WP camshafts to make serious, reliable power.

What's Included:

  • S&S 4.320" Cylinders: Ductile iron liners, updated fin profile, texture black or black granite with machined highlights. Stock bolt pattern. No case mods required.

  • Forged Pistons: Engineered for high-compression durability.

  • Cometic MLS Head and Base Gaskets: Multi-layer steel for reliable sealing in high-performance applications.

  • Ring gaps pre-set by us on a precision diamond ring filer. Bolt them in and go. No hours at the bench with a file and feeler gauge.

  • Proudly Made in the USA.

Starting at $1.885.00

Start Your Order For The 132"/136" Big Bore Kit Online

Cylinders:

  • Bore: 4.320"

  • Liner: Ductile iron

  • Bolt Pattern: Stock (no case mods required)

  • S&S Part Number: 920-0162

  • Compatibility: 2017-up Milwaukee-Eight

Displacement Options:

  • 132": 4.320" bore × 4.500" stroke

  • 136": 4.320" bore × 4.625" stroke

Pistons:

  • Dome Volume: 0.0cc

  • Weight: 650.20g per assembly

Compression:

At .040" piston-to-head clearance

  • 11.7:1 with 88cc chamber

  • Metal pistons, one with a 'Wizzard' logo, made of shiny aluminum with a smooth, reflective surface.

    Forged Pistons and Pre-Set Rings

    Pre-set ring gaps using precision diamond ring filer for easy installation.

  • A black gasket for an engine, placed on a white box with black and white 'Cometic' branding.

    Cometic MLS Head and Base Gaskets

    High performance multi-layer-steel composition. Reliable sealing for high-performance builds.

  • A close-up of an automotive engine cylinder head with black and silver metallic parts.

    Optional CNC Ported Heads

    Available with Ward CNC ported heads for maximum airflow and power.

  • Metal camshaft with multiple lobes and gear, used in an engine

    Optional High Performance Camshafts

    This kit pairs perfectly with one of our high-performance Ward camshafts, designed to maximize power and torque where it matters most