Porsche WR Big Valve Kit 42/36 for 356 (1955-1965) and 912 (1966-1969).

The newest WR Ultimate Performance 42/36 Big Valve Kit is engineered specifically for OEM 356 and 912 cylinder heads, delivering everything needed to convert stock heads for use with our 91mm piston and cylinder set. It’s also an excellent choice for preparing stock-bore heads for high-rpm street or race applications.

At the heart of the kit are custom 8mm stem intake and exhaust valves, manufactured by Manley exclusively for WR to withstand the added heat and demands of air-cooled performance engines. Upgraded single-groove locks outperform factory three-groove designs by eliminating retainer wear, while hardened steel valve seats are unleaded-fuel compatible and require minimal machine work.

The valves are designed to run hardened 2mm lash caps, providing a larger rocker contact area while ensuring correct valve train geometry and full valve lift. WR Locking Valve Guides feature Viton intake seals and a unique locking ridge that works with 4340 chromoly spring pads to secure the guide in place while centering the inner spring.

WR Dual Valve Springs support a wide range of cam profiles—from .325" to over .500" lift—and are stable beyond 7,000 RPM. Complementing them are lightweight WR Chromoly Retainers, purpose-built for long life and high-performance operation.

This is not an off-the-shelf parts package. Every component is made in the USA and developed, tested, and refined through dozens of engine builds to deliver a proven combination you can trust. For 356 and 912 performance, this is a no-compromise solution.

Complete Kit Includes:

4 x 42mm Stainless Manley Intake Valves with Lash Caps
4 x 36mm Stainless Manley Exhaust Valves with Lash Caps
4 x WR Locking Intake Guides with Viton Seals
4 x WR Locking Exhaust Guides
8 x WR High-Performance Dual Valve Springs
8 x WR Chromoly Spring Pads
8 x WR Chromoly Retainers
16 x Manley Single-Groove Valve Locks
4 x 42mm Hardened Steel Intake Seats
4 x 36mm Hardened Steel Exhaust Seats
Complete setup instructions covering valve tip height, spring pressure, plus recommended porting and chamber modifications.

Willhoit Auto Restoration

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Porsche WR Big Valve Kit 42/36 - 356 - 912 | 1955-1969 WR-423-600-00