Spring Shims - 1.040 OD .030 Thick

PAC RACING SPRINGS Spring Shims - 1.040 OD .030 Thick are precision-engineered valve train components designed for high-performance engine builders and racers who demand exact spring rate control. These shims serve as critical adjustment tools in dual-spring and single-spring valve configurations, allowing tuners to fine-tune spring preload and maintain optimal valve lift characteristics across varying RPM ranges. Whether you're building a competition engine, restoring a classic muscle car, or optimizing an existing platform, these shims provide the precision needed to achieve target spring pressures.

Manufactured by PAC RACING SPRINGS, a respected OEM and performance supplier, these shims feature a 1.040-inch outer diameter with a .030-inch thickness—specifications that make them compatible with most modern valve spring assemblies using standard spring seats. The precise .030-inch thickness allows for incremental adjustments to spring pressure without excessive material removal or complicated machining. PAC's manufacturing tolerances ensure consistent performance across multiple shims, critical for maintaining balanced valve train geometry and preventing coil-bind or insufficient spring tension that could compromise cam lobe protection and valve control.

Engine builders, performance shops, and motorsports enthusiasts benefit most from these shims when dialing in custom valve spring pressures for cammed engines, turbo applications, or naturally aspirated builds requiring elevated RPM capability. Weighing only 0.09 lbs per shim, they add negligible mass while delivering measurable tuning flexibility. Installation involves removing the valve spring retainer, placing the shim on the spring seat, and reassembling—a straightforward process that requires basic engine work knowledge. These shims are essential inventory for any serious performance engine program where valve train reliability and tuning precision are non-negotiable.