Star Racing Cam Selection Guide
The Two Questions That Determine Everything
Before you look at a single cam spec, answer these two questions honestly:
- What engine are you running?
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Stock Milwaukee-Eight (M8), 107–121 cubic inches, no internal modifications
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Big-inch Built M8 with big-bore kits — 124+ cubic inches
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Twin Cam, chain-drive, 2007-2016
- What have you done to the engine, and what are you willing to do?
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Stock internals, want a bolt-on — no spring upgrades, no machine work
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Stage 1 mods (exhaust, air cleaner) but stock internals
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Full build — experienced builder, proper machine work, professional tuning
Your answers to these two questions narrow the field immediately. Everything else — lift numbers, duration, RPM range — flows from there.
How to Read a Cam Spec (Without Getting Lost)
You'll see three numbers repeated throughout this guide. Here's what they actually mean in plain terms:
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Lift — How far the cam opens the valve. More lift means more airflow potential. But more lift also means more stress on springs, retainers, and the valvetrain. More isn't always better — it has to match your engine's ability to use it.
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Intake Valve Close (IVC) — When the intake valve closes relative to the piston's position. This is one of the most important numbers in cam selection, and most people ignore it. A cam that closes the intake valve early traps more air at low RPM, which is great for street torque. A cam that holds it open longer builds more top-end power — but at the cost of low-end response. This number tells you where in the RPM range the cam is optimized.
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RPM Powerband — The range where this cam does its best work. Match this to how you actually ride the bike. A cam with a 3,000–7,000 RPM powerband on a street bike that never sees above 4,500 RPM is a waste of money and a worse riding experience.
Star M8 Cam Overview
Milwaukee-Eight Cams — Stock Engine Builds
For riders running 107 - 121 cubic inch M8 engines with stock internals.
The good news: you have real options here, and the right choice depends on how aggressive you want to go — not on how much machine work you're willing to do. All three of these cams are compatible with stock pistons.
Star 30/30 — .485 Lift | 1,700–5,500 RPM
The one that started it all. The 30/30 is our best-selling cam — and it's held that position for good reason. It's the biggest bolt-on cam available for the stock M8 platform. No spring upgrades. No machine work. No internal modifications of any kind.
What makes the 30/30 different is its dual-lobe profile — a torque-focused intake lobe paired with a mid-range exhaust lobe. The result is a power curve that pulls hard from the bottom and keeps building through the mid-range. With an intake valve close of 25° ABDC, this cam is engineered to trap air early and maximize cylinder filling right where street riding actually happens. You'll know it's working the moment you start the bike. That beautiful chopping idle isn't just sound — it's a function of the cam profile doing exactly what it was designed to do.
Best for: Riders who want excellent bolt-on performance from a stock engine. If you're not planning engine work and want the most the stock platform can give you — start and end here.
Compatibility: All M8 models (recommended for 107-117 cubic inch displacement). Requires no valve spring or lifter guide upgrades.
Star M28 — .540 Lift | 2,000–5,500 RPM
More lift. More aggression. Designed specifically for the M8 Gen II platform (2024-2026 models). The M28 is the next step up from the 30/30 — more lift, a broader power curve, and an even more aggressive idle. With .540 lift and an IVC of 28° ABDC, it delivers more top-end capability than the 30/30 while maintaining real street torque from 2,000 RPM. The dual-lobe design works the same way — intake side optimized for low-RPM torque, exhaust side tuned for top-end power. But the M28 pushes further into both ends of that range. The M28 can run in Gen 1 M8 engines, but spring and lifter guide upgrades are required for those applications. On Gen 2, it runs stock-compatible springs.
Best for: Riders who want to push beyond the 30/30 without a full engine build. Especially well-suited for Gen 2 M8 owners looking to maximize what the platform offers before committing to bigger displacement.
Compatibility: Gen 2 M8 (2024–2026) — stock valve springs compatible, lifter guide upgrade required. Recommended 117-121 cubic inch displacement. Gen 1 M8 (2017–2024) — valve spring (640SK) and lifter guide (M8726LG) upgrades required. Recommended for 107-117 cubic inch displacement.
Star F35A — .572 Lift | 2,300–6,500 RPM
The F35A represents everything we could engineer into a cam that still fits a stock M8 engine - .572 lift, an IVC of 35° ABDC, and a powerband that pulls hard from 2,300 RPM and keeps building all the way to 6,500. This cam was built in the spirit of the legendary 30/30 — same short-duration philosophy, engineered to trap air and maximize cylinder filling — but with .087 additional lift and an extended RPM range. If you want every bit of performance a stock engine can deliver without opening it up, this is that cam. Note - the F35A can fit in up to 128 cubic inch "built" engine.
Best for: Riders who are maxing out a stock engine and want the most aggressive option the platform will support without internal modifications.
Compatibility: All M8 models (recommended for 114-128 cubic inch displacement) — valve spring (640SK) and lifter guide (M8726LG) upgrades required.
Milwaukee-Eight Cams — Built Engines
For riders running big-bore kits. 124–150 cubic inch M8 builds.
Once you've opened the engine up, the stock cam selection no longer applies. Built engines breathe differently, rev differently, and demand a cam profile that matches the displacement and the build intent. This is where cam selection gets more consequential — and where getting it wrong costs you real performance.
All cams in this section require spring and lifter guide upgrades. Professional installation and tuning is strongly recommended.
Star 3/4 Race — .585 Lift | 2,500–6,500 RPM
If you've built a 128–143 cubic inch M8 and you're not sure where to start — start here. The 3/4 Race is one of our best-selling camshaft across the entire lineup, and it's earned that position by doing exactly what a built engine needs: delivering the most lift available for reliable, street-driven performance across a broad powerband - .585" lift, an IVC of 42° ABDC, and a dual-lobe design that combines low-to-mid range torque on the intake side with top-end power on the exhaust side. The result is a cam that pulls hard from 2,500 RPM and keeps building to 6,500 — the full range of what a serious 128–143 inch build demands.
Builders across the M8 platform continue to put this cam in more and more engines because it performs and it holds up.
Best for: 128–143 cubic inch big-bore builds. This is the default recommendation for built M8 engines in the mid-displacement range. If you're not sure whether to go, start here.
Compatibility: All M8 models (recommended for 128-143 cubic inch displacement)— valve spring (640SK) and lifter guide (M8726LG) upgrades required.
Star F47 Fighter — .600 Lift | 2,500–6,500 RPM
The F47 Fighter is a street/race cam engineered specifically for serious big-inch M8 builds in the 131+ cubic inch range. With .600" lift and an IVC of 47° ABDC — the most aggressive duration profile in the street-oriented portion of our lineup — the F47 extracts maximum power across the full RPM range from street riding to all-out performance. The dual-lobe design works across both ends of the range: low-to-mid range torque on the intake side, top-end power on the exhaust side. But at 131+ cubic inches, there's enough displacement to actually use everything this cam has to offer. At that level with a proper build behind it, the F47 is the right tool. If you're at 124–128 inches, the 3/4 Race is still the better match.
Best for: 131–143 cubic inch big-inch M8 builds. Riders who want genuine street/race capability from a large-displacement build.
Compatibility: All M8 models (recommended for 131+ cubic inch displacement) — valve spring (640SK) and lifter guide (M8726LG) upgrades required.
Star Full Race 2.0 — .627 Lift | 3,000–7,000 RPM
The Full Race 2.0 is the most powerful camshaft in the Star cam lineup. At .627" lift, an IVC of 54° ABDC and a powerband that runs from 3,000 to 7,000 RPM, it's purpose-built for 135+ cubic inch engines that are demanding every bit of available power. An experienced builder needs to verify spring capabilities, coil bind, installed heights, and piston-to-valve clearances before startup. Done right, the Full Race 2.0 delivers a true racing cam sound and a powerband that dominates from 3,000 RPM to redline.
Best for: Maximum-performance big-inch builds. Experienced builders. Engines and riders that are genuinely ready for race-level cam profiles.
Compatibility: All M8 models (recommended for 135+ cubic inch displacement) — valve spring (640SK) and lifter guide (M8726LG) upgrades required. Experienced installer required. Professional tuning required.
M8 Cam Comparison Table
Star Twin Cam 2007+ Cam Overview
For Twin Cam engines 96, 103, 107, 110, 113, and 117 cubic inch applications. The Twin Cam platform is different from the M8 in some important ways — different valve train geometry, different breathing characteristics, different RPM behavior. Cams that work on an M8 don't translate directly. These three cams were developed specifically for the Twin Cam platform and the riders who are still building on it.
Star Torkstar 577 — .577 Lift | 2,000–5,000 RPM
Real performance with no engine work. The Torkstar 577 is the Twin Cam equivalent of the 30/30 — a true bolt-in upgrade that delivers meaningful performance gains without touching the engine internals. Designed for stock and Stage 1 builds on 96, 103, and 110 cubic inch chain-drive Twin Cam engines, it works with stock valve springs and delivers a broad, satisfying midrange powerband right where everyday riding happens.
With .577" lift, a 32° IVC, and a 224 x 248 duration profile, this cam adds real performance to a stock or mildly modified Twin Cam engine — and it sounds exactly like a Harley should while doing it.
Best for: Stock and Stage 1 Twin Cam builds where simplicity matters. If you want the biggest performance improvement you can make on a stock Twin Cam without cracking the engine open — this is it.
Compatibility: Chain-drive Twin Cam, 2007 and up, 96-110 cubic inch displacement recommended. Stock valve springs compatible.
Star P38 Lightning 615 — .615 Lift | 2,500–5,500 RPM
The P38 Lightning is for riders who've outgrown the Torkstar 577 and want a little more. With .615" lift, a 38° IVC, a 235 x 255 duration profile, and compatibility across a wide displacement range — 103 through 117 cubic inch piston kit builds — the P38 extracts strong, reliable performance from Twin Cam engines that have room to breathe. Before installation, verify that your existing valve springs are rated to handle up to .620 lift. This is the key installation consideration. If your springs aren't there, upgrade them before this cam goes in. We recommend our TC Spring Kit (TC20-20350) as an easy bundled upgrade. You will also need piston upgrades and deeper valve pockets.
Best for: Riders stepping up from the Torkstar, or building a more serious 103–117 cubic inch Twin Cam engine where the additional lift and displacement range make sense.
Compatibility: Chain-drive Twin Cam, 2007 and up, 103–117 cubic inch displacement recommended. Valve springs must be rated to .620" lift minimum (TC20-20350 recommended).
Star Thrasher 650 — .650 Lift | 2,500-6,500 RPM
The most aggressive cam in the Twin Cam lineup. The Thrasher is the top of the Star Twin Cam lineup — high-lift, high-output, and built for serious Twin Cam builds across any displacement. With .650" lift, a 40° IVC, and a 240 x 260 duration profile, this cam pushes well beyond bolt-on performance into genuine build territory. Aftermarket pistons, springs and deeper valve pockets are required. Piston-to-valve clearance must be verified by an experienced builder before startup. Done right, the Thrasher delivers the kind of aggressive, high-output performance that serious Twin Cam builds are built around.
Best for: High-performance Twin Cam builds where maximum lift and output are the goal. Not a street-mild cam — this is for riders who are building for performance and have the engine to back it up.
Compatibility: Chain-drive Twin Cam, 2007 and up, 103-117 cubic inch displacement recommended. Spring upgrade required (TC20-20350 recommended). Piston-to-valve clearance verification by experienced builder required. Professional tuning required.