S&S 551 vs S&S 510 — torque cam or power cam?
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: 4700 rpm, limited by cam.
Where each one wins
| RPM | S&S 551 | S&S 510 | diff |
|---|---|---|---|
| 2000 | 97 | 97 | +0 |
| 2500 | 102 | 104 | +1 |
| 3000 | 106 | 110 | +4 |
| 3500 | 108 | 114 | +6 |
| 4000 | 102 | 114 | +12 |
| 4500 | 94 | 109 | +14 |
Torque, lb-ft, at the rear wheel. Everything except the part named is identical between the two runs.
This is the cleanest illustration of the trade on the whole Twin Cam cam chart, and the peak horsepower numbers are badly misleading on their own.
The 551 is a torque grind: short intake duration, high lift, and a published range that ends early — so the rev ceiling on this page is set by the camshaft, not the engine. The 510 keeps pulling much further up and takes a far larger peak with it.
Read the delta table before deciding the 510 wins. Down where a loaded bagger actually lives, the shorter grind is not behind — and a cam that makes its power where you never ride is a cam you paid for and cannot use.
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 | S&S 551 · 216/238 dur · 0.550" 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 | 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 | 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) |