COMP Cams K31-600-9 Thumpr 227/241 Hydraulic Roller & Evolution Lifter K-Kit for Ford 221-302

The COMP Cams K31-600-9 is a complete Thumpr Series hydraulic roller camshaft K-Kit designed for small block Ford (SBF) 221, 260, 289, and 302 cubic inch engines. This updated K-Kit pairs COMP Cams' proven Thumpr cam grind with their next-generation Evolution hydraulic roller lifters, delivering the signature aggressive thumping idle and strong street performance in a comprehensive all-in-one package.

The Thumpr grind profile features an early exhaust valve opening, extended exhaust duration, and a generous overlap between intake and exhaust events — engineered specifically to produce that classic, choppy muscle car idle sound without sacrificing real-world driveability. The hydraulic roller design delivers a meaningful power advantage over comparable flat tappet grinds while maintaining everyday reliability and low maintenance.

Camshaft Specifications:

• Cam Series: Thumpr
• Cam Type: Hydraulic Roller
• Intake Duration @ .050" Lift: 227°
• Exhaust Duration @ .050" Lift: 241°
• Advertised Intake Duration: 283°
• Advertised Exhaust Duration: 303°
• Intake Valve Lift: 0.531"
• Exhaust Valve Lift: 0.515"
• Lobe Separation Angle: 107°
• Basic Operating RPM Range: 1,900–5,600 RPM
• Camshaft Material: Austempered Ductile Iron

K-Kit Includes:

• Hydraulic roller camshaft
• COMP Cams Evolution hydraulic roller lifters
• Valve springs
• Retainers
• Valve locks (keepers)
• Valve stem seals
• Timing chain set
• Decals and installation instructions

Usage Notes: Suitable for high-performance street use. Compatible with stock torque converter, but performs best with a 2,000+ RPM stall converter and performance rear gears. Produces a choppy, thumping idle characteristic of a purpose-built street/performance build.