One of the most common problems with reconditioned engines is an increase in compression values, which can cause additional heat to be generated in your combustion chamber. This Head Shim from Permaseal Gaskets is designed to combat that possibility, helping you to avoid overheating problems. Permaseal Gaskets' Head Shims have been envisioned as a cost-effective way to restore the compression values that can be caused by metal being removed from the face of the head and cylinder block.