COMP Cams CL42-601-11 Mutha' Thumpr 235/249 Hydraulic Roller Cam and Lifter Kit for Oldsmobile 260-455

The COMP Cams CL42-601-11 Mutha' Thumpr Retro-Fit Hydraulic Roller Cam and Lifter Kit is engineered to deliver the classic muscle car idle sound with serious street/strip performance for Oldsmobile 260-455 V8 engines. With advertised duration of 291/311 degrees and valve lift of 0.540" intake / 0.532" exhaust, this camshaft produces an aggressive, choppy idle that turns heads while delivering meaningful horsepower and torque gains across the RPM range.

The Mutha' Thumpr grind uses a specially engineered lobe profile that combines an early intake valve opening with extended exhaust duration and generous intake/exhaust overlap. This design maximizes the signature loping idle character without sacrificing drivability on the street. The retro-fit hydraulic roller design brings modern roller-cam technology to classic Oldsmobile engines that originally used flat-tappet camshafts.

Key Specifications:

• Advertised Duration: 291° Intake / 311° Exhaust
• Duration at 0.050": 235° Intake / 249° Exhaust
• Valve Lift: 0.540" Intake / 0.532" Exhaust
• Cam Type: Retro-Fit Hydraulic Roller
• Application: Oldsmobile 260, 307, 350, 400, 403, 425, and 455 V8

Recommended Supporting Modifications:

• Minimum 9:1 compression ratio
• 2,500+ RPM stall speed torque converter
• Performance intake manifold
• Rear-end gears optimized for performance
• Headers

Kit Includes:

• Mutha' Thumpr retro-fit hydraulic roller camshaft
• Hydraulic roller lifters
• Assembly lube
• COMP Cams decals
• Installation instructions

This kit is best suited for high-performance street and strip use where an aggressive idle quality, strong mid-to-upper RPM power, and the iconic muscle car sound are the priority. COMP Cams' Mutha' Thumpr series is a proven choice for classic Oldsmobile builds looking to maximize performance with a retro-fit roller valvetrain upgrade.