Cruiser Valve Shims

Frequently Asked Questions

• What are valve shims and why do cruiser engines use them?

  Valve shims are thin, precision discs used in shim-under-bucket valvetrains to adjust valve lash by replacing the existing shim with a calculated thickness, and cruisers commonly use this design for reliable, low‑maintenance operation and precise valve timing.
• How do I choose the correct shim diameter and thickness for my cruiser?

  Match the shim diameter to your valve bucket, verify the old shim marking with a micrometer, and cross-check required clearance and sizes against your service manual before selecting a kit.
• How do I calculate the new shim thickness I need?

  Use the service manual formula—New shim = (measured clearance − specified clearance) + old shim thickness—and then select the closest available shim size, aiming for a slightly looser clearance and rechecking after installation.
• What materials and kit features should I look for in cruiser valve shim kits?

  Choose kits made from durable materials rated for valvetrain stress, built to manufacturer-specified tolerances, and that include a range of diameters and extra thicknesses to allow iterative adjustments.
• How often should shims be inspected and what install/maintenance cues should I watch for on a cruiser?

  Inspect shims at regular valve service intervals and sooner with aggressive riding; watch for noisy valvetrain, changing clearances, or unusual valve behavior, and use proper measuring tools with a recheck after install to extend service life.