How to get 100 hp out of a Twin Cam 103
Simulated rear‑wheel horsepower and torque — measured after the primary drive, clutch and transmission, the same way a chassis dyno reads a bike. These are not flywheel numbers, and they are not directly comparable to a manufacturer’s crank rating. Rev ceiling for this combination: 5500 rpm, limited by engine.
Triple digits at the rear wheel on stock displacement. No big bore, no stroker crank, no power adder — a camshaft, ported heads, forged flat-tops and a matched tune.
The three parts that matter are in the top end. The cam sets where the engine will make power, the head work decides how much air it can use up there, and the tune lets it happen. Everything else in the list is there to support those three safely.
The lifters are not a detail. A build that revs past where the stock hydraulic units are happy needs short-travel units, and the rev ceiling on this page reflects the ones in the parts list.
The build
| Engine | TC103 (2010 CVO / 2012+) 3.875 × 4.375 |
|---|---|
| Crank / balancer | A motor — non-balanced (Dyna / Touring / CVO) |
| Pistons | Forged flat-top (11cc combustion gain) |
| Head gasket | Cometic .030" — neutral baseline |
| Cylinder heads | STOCK -06 + S&S CNC port service · 1.9/1.575 |
| Porting | Stage 2 CNC port (full) |
| Camshaft | S&S 510 · 238/252 dur · 0.510" lift |
| Valve springs | Stock springs (as fitted to the heads) |
| Rocker arms | Stock rocker arms — 1.625:1 |
| Pushrods | Stock pushrods |
| Lifters | Short-travel hydraulic (Feuling/Andrews) |
| Induction | HPI / SE 55mm throttle body |
| Exhaust | 2-into-1 stepped (D&D FatCat / E-Series) |
| Air cleaner | Screamin' Eagle / Stage I high-flow |
| Tune | Dyno-tuned (matched to build) |
| Power adder | None (naturally aspirated) |