COMP Cams CL42-602-11 Big Mutha' Thumpr 243/257 Hydraulic Roller Retro-Fit Cam & Lifter Kit

The COMP Cams CL42-602-11 Big Mutha' Thumpr is an aggressive hydraulic roller retro-fit camshaft and lifter kit engineered for Oldsmobile 260-455 V8 engines. Built for serious street/strip duty, this cam delivers the signature lopey, hard-hitting idle and exhaust note that muscle car and street rod builders demand—backed by real horsepower gains and a broad torque curve.

Camshaft Specifications:

• Duration @ .050" Lift: 243° Intake / 257° Exhaust
• Valve Lift: .552" Intake / .537" Exhaust
• RPM Operating Range: 2,300–6,100
• Cam Type: Hydraulic Roller Retro-Fit

Performance Profile:

• Early intake valve opening and long exhaust duration create optimum overlap for a powerful, hard-hitting exhaust note
• Excellent horsepower gains with a broad torque curve — ideal for muscle cars and street rods
• Requires minimum 9.5:1 compression ratio
• Requires 2,800+ RPM stall converter
• Requires aftermarket intake manifold, headers, and numerically higher rear gear ratio
• Produces a very rough, aggressive idle — not a stock-replacement grind
• Minimal engine vacuum — modifications required for vacuum-operated accessories such as power brakes
• Must be used with upgraded valvetrain components including COMP Cams valve springs and roller rockers

Kit Contents:

• Hydraulic Roller Retro-Fit Camshaft
• Matching Hydraulic Roller Lifters
• Assembly Lube
• Decals
• Installation Instructions

COMP Cams manufactures this camshaft to precise tolerances as part of their Thumpr series, which offers three distinct grind levels — Thumpr, Mutha' Thumpr, and Big Mutha' Thumpr — allowing builders to select the right intensity for their combination. The CL42-602-11 represents the most aggressive grind in the lineup, delivering maximum sound and performance for dedicated performance builds.