Milwaukee-Eight Stage 1 and Big Bore Upgrades: 107 to 114, 117, and Beyond
Thinking about more power from your Milwaukee-Eight? Here's how Stage 1 tuning and big bore kits work, what each stage actually delivers, and how to plan a build that doesn't outrun your budget.
The Milwaukee-Eight responds well to performance upgrades — its four-valve heads and improved breathing over the Twin Cam give tuners more to work with. But "Stage 1," "Stage 2," and big bore kits mean different things depending on who's selling them, and it's easy to spend money on parts that don't match your goals. Here's how the stages actually break down on an M8.
Stage 1: Breathing and Tuning
Stage 1 is the entry point and delivers the best value-per-dollar of any M8 upgrade. It typically includes:
- A high-flow air cleaner to reduce intake restriction
- A slip-on or full exhaust system for better flow
- An ECU retune (via a tuner like a Power Vision or dealer-level tune) to match the new airflow
No internal engine work is required. Expect a noticeable torque and throttle response improvement, particularly in the low-to-mid RPM range where most street riding happens.
Stage 2: Cams and Cylinder Heads
Stage 2 adds a performance camshaft and often mild head porting on top of the Stage 1 changes. This requires removing the rocker boxes and cam chest — more labour, but no engine splitting. A quality cam swap on an M8 can add meaningful mid-range and top-end power, but it changes the powerband character, so we always discuss riding style before recommending a specific grind.
Stage 3 and Big Bore Kits
Stage 3 typically means displacement — big bore cylinder and piston kits that take a 107 to 114cc-equivalent or larger, sometimes paired with the 114 or 117 stroker crank for even more displacement. This is the most involved and most expensive stage, requiring case splitting or at minimum cylinder/piston replacement, and always needs a corresponding ECU retune. It delivers the biggest power gain but also the biggest bill.
| Stage | Typical Work | Approx. Power Gain |
|---|---|---|
| Stage 1 | Air cleaner, exhaust, retune | 8–12% |
| Stage 2 | + cams, mild head work | 15–20% |
| Stage 3 | + big bore / stroker | 25%+ |
Most riders who come in wanting "big power" are genuinely happiest with a well-tuned Stage 1 — it's the upgrade that's noticeable every single ride, not just at wide-open throttle on a back road outside New Glasgow.
Every stage beyond Stage 1 benefits from a dyno session to verify the tune rather than guess at it. We handle the full range from a simple exhaust swap to a complete big bore build — come in for a consultation and we'll help you pick the stage that actually matches your riding.
Need This Service in Pictou County?
Our shop handles everything described in this article. Book a service appointment or call us with questions.