These Mr. Gasket cam buttons are an absolute necessity for roller cam installations and useful to maintain accuracy in any cam installation. Cam buttons keep the camshaft from moving in and out and causing erratic timing.

A camshaft button, or camshaft thrust bumper installs into the hole in the front end of the camshaft and prevents camshaft walk in roller camshaft applications. Flat tappet cams are ground with a small angle in the lobes that puts a side load on the camshaft. Without this a camshaft has a natural tendency to move or walk, out of the block when rotating. Roller cam lobes can't be ground that way so engines originally equipped that way usually use a retainer plate to secure them. The camshaft button serves the same purpose, but it does so by contacting the timing cover to prevent movement. If you have an engine already converted, a worn or missing cam thrust bumper will result in too much end play, resulting in erratic timing and should be checked.