Big, Bad Brute: S&S Announces MK136 Crate Engine

Towards the end of 2023, we told you about S&S Cycle’s new 136ci big-bore kit, intended to swap into Harley-Davidson Milwaukee Eight cases, or S&S’s own MK-series cases. Now, S&S has taken this program to the next logical step, and is offering a complete drop-in MK136 crate engine.

Here’s the official description of the upgrades involved, from S&S:

Cylinder Heads

  • High-flow cylinder heads with premium seats, guides, valves, springs, and seals
  • +1mm oversized intake and exhaust valves
  • Valves are .030” longer than stock for improved valve-train geometry
  • .605” max lift valve springs
  • High-strength alloy used in cylinder head casting, improved strength at high temperatures
  • Enlarged cooling passage around the exhaust seats • S&S Exclusive breather boxes


  • Forged pistons
  • S&S performance oil pump and cam support plateP
  • Premium tappets and tappet cuffs
  • Billet aluminum covers • Sprocket shaft spacer included
  • Champion spark plugs • Retains stock engine height
  • Includes Cam Cover Badge
  • Powder coat finish matches factory finish
  • Huge displacement increase means a huge power increase


  • All premium quality components
  • Patented Dual-Spray Piston Cooling Jets
  • Precision machined oil scraper
  • Enlarged oil sump
  • Contoured floor allows oil to easily drain back to the sump

With just the big bore kit, S&S said proper tuning and pairing with performance exhaust and intake could see the 136ci top end pumping out 150 horsepower. The video above rates this engine for 121 horsepower and 145 pound-feet of torque. Note that S&S also sells a “race-only” version of the engine with a different cam installed, and it is likely that machine makes much more jam.

Both engines come with a one-year warranty and an $11,995 USD MSRP for American customers. We’ve seen no Canadian price tag yet, but after the exchange rate and taxes, you’re going to be looking at close to $20,000 CAD…

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