S&S 510 vs Andrews TW37B
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 | S&S 510 | Andrews TW37B | diff |
|---|---|---|---|
| 2000 | 97 | 99 | +2 |
| 2500 | 104 | 106 | +2 |
| 3000 | 110 | 111 | +1 |
| 3500 | 114 | 115 | +1 |
| 4000 | 114 | 113 | -1 |
| 4500 | 109 | 107 | -2 |
| 5000 | 101 | 99 | -2 |
| 5500 | 95 | 92 | -2 |
Torque, lb-ft, at the rear wheel. Everything except the part named is identical between the two runs.
These two land in the same shopping cart constantly, and the peak numbers come out close enough that the peak is the wrong thing to choose on.
The difference is distribution. Read the delta table row by row: one of them is ahead through the middle of the range and the other claws it back at the top. Which one suits you depends entirely on gearing, weight and how you ride.
Both need a spring kit and both want the tune redone afterwards. Neither is a drop-in-and-forget part, whatever the catalogue implies.
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 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) |
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 | 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) |