1.640 O.D. Spring Shims .635 I.D. .015 Thickness

The 1.640 O.D. Spring Shims .635 I.D. .015 Thickness by COMP CAMS are precision valve spring shims engineered for engine builders and performance enthusiasts who demand exact valve train geometry. These shims address a critical requirement in high-performance and rebuilding applications: fine-tuning valve spring installed height to achieve optimal preload and prevent coil bind. Available as a set of 16 units, this product serves both professional engine shops and serious DIY builders who understand that valve spring shimming directly impacts engine reliability, horsepower delivery, and longevity.

Manufactured from hardened steel, the 1.640 O.D. Spring Shims feature a .015-inch thickness with a .635-inch inner diameter designed to stack under valve springs without degradation or creep during extended operation. The tight dimensional tolerances ensure consistent preload across the entire valve train, preventing spring surge and maintaining consistent valve timing under high RPM conditions. Each shim's compact profile allows stackable configuration, enabling builders to dial in exact spring heights in 0.015-inch increments—critical for tuning applications where even marginal variations affect cam profile effectiveness and valve control.

These shims are essential for anyone modifying or assembling high-revving engines, particularly small-block and big-block platforms where aftermarket cam kits demand precise installed height verification. Installation requires removal of the valve spring, careful measurement of existing height, and stacking shims to achieve manufacturer-specified preload ranges. The set of 16 provides adequate inventory for multi-cylinder engines or allows spare material for future rebuilds, making this a practical addition to any serious engine builder's toolkit.