Stage IV vs Twin Cam Bolt-On: Which Harley-Davidson Engine Upgrade Is Right for You?
Two Great Upgrades, Two Different Riders
When customers walk into New Castle Harley-Davidson asking about performance upgrades, two kits come up more than any other: the Screamin' Eagle Stage IV Street Performance Kit for Sportster Models and the Screamin' Eagle Twin Cam Bolt-On 110ci to 117ci Kit. Both are serious performance investments. But they're built for completely different bikes and riding goals.
Here's a clear breakdown to help you decide.
The Screamin' Eagle Stage IV Street Performance Kit (Sportster)
The Stage IV Street Performance Kit is designed specifically for Harley-Davidson Sportster models. It's a comprehensive bolt-on upgrade that transforms the Sportster's engine into a high-output street machine.
- Compatible with: Harley-Davidson Sportster models
- What you get: Increased displacement, optimized airflow, and fueling upgrades — all engineered to work together as a system
- Power character: Strong low-to-mid range torque with improved top-end pull
- Price: $3,149.95
Best for: Sportster riders who want the maximum bolt-on performance available for their platform without swapping to a crate engine.
Shop the Stage IV Sportster Kit →
The Screamin' Eagle Twin Cam Bolt-On 110ci to 117ci Kit
The Twin Cam Bolt-On 110ci to 117ci Kit is built for a different class of Harley entirely — the big Twin Cam-powered models like Touring and Softail bikes running the 110ci engine.
- Compatible with: Twin Cam-powered Harley-Davidson models with 110ci engines (Touring, Softail, and select others)
- What you get: A displacement jump from 110ci to 117ci using bolt-on components — no full engine teardown required
- Power character: Massive torque increase, especially noticeable when two-up riding or pulling weight
- Price: $2,449.95
Best for: Touring and Softail riders who want more grunt for highway riding, loaded touring, or two-up use — without the cost of a full crate engine.
Shop the Twin Cam Bolt-On Kit →
Side-by-Side Comparison
| Feature | Stage IV Sportster Kit | Twin Cam 110→117ci Kit |
|---|---|---|
| Compatible bikes | Sportster models | Twin Cam Touring & Softail |
| Upgrade type | Full Stage IV system | Displacement bolt-on |
| Installation complexity | Moderate | Moderate |
| Price | $3,149.95 | $2,449.95 |
| Best for | Street performance | Touring & two-up power |
The Bottom Line
The choice is simple once you know your bike: Sportster riders should look at the Stage IV kit. Twin Cam Touring and Softail riders should look at the 110ci-to-117ci bolt-on. Both deliver genuine, Harley-engineered performance gains without voiding your warranty when installed by an authorized dealer.
Have questions about which kit fits your specific model year? Contact us at New Castle Harley-Davidson — we're happy to help you spec the right upgrade.
Stage IV Sportster Kit – $3,149.95
Twin Cam Bolt-On Kit – $2,449.95