COMP Cams 42-602-11 Big Mutha' Thumpr 243/257 Hydraulic Roller Camshaft for Oldsmobile 260-455

The COMP Cams 42-602-11 Big Mutha' Thumpr is a retro-fit hydraulic roller camshaft engineered for Oldsmobile 260-455 V8 engines originally equipped with flat tappet camshafts. This aggressive street/strip grind delivers the classic muscle car idle sound combined with real performance gains, making it a top choice for Oldsmobile performance builds.

The Thumpr series lobe profile uses a combination of early exhaust valve opening, extended exhaust duration, and generous intake/exhaust overlap to maximize rough-idling characteristics — producing a hard-hitting, aggressive exhaust note without sacrificing engine power output or street drivability. The hydraulic roller design delivers a substantial power advantage over an equivalent flat tappet grind while maintaining everyday reliability and easy maintenance.

Camshaft Specifications:

• Advertised Duration: 299° Intake / 319° Exhaust
• Duration @ .050" Lift: 243° Intake / 257° Exhaust
• Valve Lift: .552" Intake / .537" Exhaust
• Lobe Separation Angle: 107°
• RPM Operating Range: 2,300–6,100 RPM
• Cam Type: Retro-Fit Hydraulic Roller
• Usage: Street/Strip

Recommended Supporting Modifications:

• Minimum 9.5:1 compression ratio
• 2,800+ RPM stall speed torque converter
• Performance intake manifold
• Rear end gears appropriate for RPM range
• Headers
• Upgraded valve springs (required)
• Vacuum accessories (power brakes, etc.) will require modifications due to reduced engine vacuum

Sold as a camshaft only. Compatible with 1967 and later Oldsmobile 260, 307, 350, 400, 403, 425, and 455 cubic inch V8 engines.