Valve lash is the distance between rocker arm and the tip of the valve stem. Proper adjustment of valve lash is very important to ensure engine life and maximize its’ efficiency. There are many detailed guides online on how to properly adjust valve lash. For tips on how to adjust valve lash and make sure it is correct, research online sites such as the COMP Cams® article on valve lash found at the following web address.http://www.cpgnation.com/forum/comp-cams-how-valve-lash-adjustment-2076.html