Shim Kit - 1.250 Dia.

The Shim Kit - 1.250 Dia. from PAC Racing Springs is a precision valve spring shim assembly designed for high-performance engine builders and racing enthusiasts who demand exact valve train geometry. Valve spring shims are critical components that sit between the spring and the cylinder head, allowing technicians to fine-tune spring seat pressure and maintain proper clearances in modified or stock engine builds. This kit exists to eliminate guesswork during engine assembly and ensure consistent performance across multiple engine configurations.

Manufactured from durable steel with a 1.250-inch outer diameter and 0.570-inch inner diameter, this shim kit includes four different thickness options—0.015, 0.020, 0.030, and 0.050 inches—enabling precise pressure adjustments to match your specific spring requirements. The stacked approach allows builders to combine shims to achieve exact seat pressures without replacing entire spring assemblies, reducing cost and simplifying the build process. Each thickness variant is engineered to maintain dimensional stability under thermal cycling and high-RPM conditions typical of racing environments.

Professional engine builders, dyno technicians, and serious enthusiasts rely on PAC Racing Springs shim kits to validate valve train dynamics during engine development. The versatile shim selection makes this kit suitable for small-block and mid-size applications requiring the 1.250-inch diameter specification. Installation is straightforward—select the required thickness combination, place the shims under the spring seat, and torque the retainer per engine specifications. Compatibility depends on your specific cylinder head design and spring seat dimensions, so verify fitment before purchase.