How much horsepower will a cam swap add?
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.
Where each one wins
| RPM | TW37B | stock cam | diff |
|---|---|---|---|
| 2000 | 99 | 86 | -13 |
| 2500 | 106 | 91 | -14 |
| 3000 | 111 | 96 | -16 |
| 3500 | 115 | 99 | -16 |
| 4000 | 113 | 95 | -18 |
| 4500 | 107 | 89 | -18 |
| 5000 | 99 | 82 | -17 |
| 5500 | 92 | 76 | -16 |
Torque, lb-ft, at the rear wheel. Everything except the part named is identical between the two runs.
Same engine, same air cleaner, same exhaust, same tune. The only change is the camshaft — and this is the change that does what every bolt-on was supposed to do.
The delta table is where to look. The cam does not simply add a number at the top; it moves the whole curve, giving up a little down low in exchange for a great deal further up, and it lets the engine keep pulling to a rev ceiling the stock grind never reached.
This is why the standing advice on a Twin Cam is cam first, everything else after. It is also why springs appear in the parts list: a cam with this much lift needs a spring kit that can follow it.
The build
| Engine | TC103 (2010 CVO / 2012+) 3.875 × 4.375 |
|---|---|
| Crank / balancer | A motor — non-balanced (Dyna / Touring / CVO) |
| Pistons | OEM cast piston (stock dome) |
| Head gasket | STOCK OEM MLS (.030" compressed) |
| Cylinder heads | STOCK 2006+ (-06 casting) · 1.805/1.575 |
| Porting | As-cast / factory (no additional work) |
| Camshaft | Andrews TW37B · 236/240 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 | Stock hydraulic lifters |
| Induction | Stock 50mm Delphi EFI (2008+) |
| 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) |
The other one
| Engine | TC103 (2010 CVO / 2012+) 3.875 × 4.375 |
|---|---|
| Crank / balancer | A motor — non-balanced (Dyna / Touring / CVO) |
| Pistons | OEM cast piston (stock dome) |
| Head gasket | STOCK OEM MLS (.030" compressed) |
| Cylinder heads | STOCK 2006+ (-06 casting) · 1.805/1.575 |
| Porting | As-cast / factory (no additional work) |
| Camshaft | Stock TC EFI (B) · 216/220 dur · 0.473" lift |
| Valve springs | Stock springs (as fitted to the heads) |
| Rocker arms | Stock rocker arms — 1.625:1 |
| Pushrods | Stock pushrods |
| Lifters | Stock hydraulic lifters |
| Induction | Stock 50mm Delphi EFI (2008+) |
| 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) |