Momentum Worx Non-VGT ISX "Chunky Charley" Valve Camshaft | DOHC CM870 / CM871 | MMWX.4298626

If you’ve converted your Cummins ISX from a VGT to a fixed-geometry turbo, you already know one of the biggest tradeoffs:

You gain simplicity and performance potential — but engine braking can take a hit when the factory VGT is removed.

The "Chunky Charley" ISX Valve Camshaft is a performance-oriented valve cam designed for DOHC Cummins ISX engines running fixed-geometry / non-VGT turbo setups.

And yes, the name fits.

Chunky Charley features 20mm-wide cam lobes compared to the older 18.5mm narrow-lobe design.

The Problem with VGT to Non-VGT Conversions

Factory VGT-equipped ISX engines use the variable turbine housing to create additional exhaust restriction during engine braking. When the VGT is removed and replaced with a fixed-geometry turbocharger, that additional restriction disappears.

The result can be:

• Reduced engine braking performance
• Weaker braking on long grades
• Less overall braking authority
• A noticeable difference when towing or hauling heavy

For trucks converted to a large-frame, T6, or other fixed-geometry turbo setup, improving the engine's internal braking characteristics becomes even more important.

The Non-VGT Solution

Chunky Charley is designed for DOHC ISX applications where stronger engine braking is desired after eliminating the factory VGT.

It features:

• 20mm-wide valve cam lobes
• Designed for DOHC Cummins ISX engines
• Ideal for fixed-geometry / non-VGT turbo conversions
• Excellent choice for large-frame and T6 turbo setups
• Designed to improve usable engine braking performance
• Installs as a drop-in upgrade
• Uses your existing factory timing wedges

No special timing wedge setup is required — installation uses the engine's existing factory timing wedges.

Thicker lobes. Bigger attitude.

That's Chunky Charley.

Why It Works

The factory VGT contributes to engine braking by creating additional exhaust restriction. Once that turbocharger is removed, a fixed-geometry setup can no longer provide the same VGT-assisted braking effect.

Chunky Charley addresses the problem through the valve camshaft and engine braking events rather than relying solely on turbocharger restriction.

The 20mm wide-lobe design also provides a larger cam-to-rocker contact area compared to the older 18.5mm narrow-lobe design.

The result is a valve camshaft well suited for performance-oriented DOHC ISX builds — especially trucks running a non-VGT turbo setup where maintaining strong engine braking matters.

Fitment

Cummins ISX DOHC / Dual Cam Engines

• CM870
• CM871
• Fixed-geometry / non-VGT turbo conversions
• Large-frame and T6 turbo conversions

Pair It With Big Betty

Replacing the injector cam at the same time?

Pair Chunky Charley with the Momentum Worx MMWX.4101432 "Big Betty" Injector Camshaft for compatible Cummins ISX DOHC applications.

Big Betty Injector Camshaft – MMWX.4101432