COMP Cams CL42-600-11 Thumpr 227/241 Retro-Fit Hydraulic Roller Cam and Lifter Kit for Oldsmobile 260-455

The COMP Cams CL42-600-11 is the entry-level grind in the Thumpr retro-fit hydraulic roller camshaft series, purpose-built for Oldsmobile 260–455 V8 engines. This kit delivers the legendary Thumpr idle sound — a hard-hitting, aggressive exhaust note — while still maintaining real-world streetability and solid power gains across the RPM range.

The Thumpr lobe profile is engineered around an early exhaust valve opening, extended exhaust duration, and a generous intake/exhaust overlap. This combination produces the signature thumping idle quality without sacrificing drivability or low-end torque. The retro-fit hydraulic roller design allows this cam to be installed in engines originally equipped with flat tappet lifters, upgrading them to a more efficient roller profile with no block modifications required.

Compared to an equivalent hydraulic flat tappet grind, the roller design delivers a measurable power increase while reducing valvetrain friction and improving long-term reliability. This is the mildest of the three Thumpr grinds — ideal for street-driven builds that want that classic muscle car sound with moderate supporting modifications.

Cam Specifications:

• Advertised Duration: 227° Intake / 241° Exhaust
• Camshaft Style: Retro-Fit Hydraulic Roller
• Lobe Separation: 107°
• Application: Oldsmobile 260, 307, 350, 400, 403, 425, 455 V8 (1967+)
• Recommended Use: Street performance with mild supporting modifications

Kit Contents:

• Thumpr retro-fit hydraulic roller camshaft
• Hydraulic roller lifters
• COMP Cams assembly lube
• Decals and installation instructions

Note: Valve springs, timing set, pushrods, and rocker arms are not included. Upgraded valve springs are recommended. Best results with a performance intake manifold, aftermarket converter, and rear gears suited to the engine's power band.