Proper piston-to-valve clearance is the difference between a winning-engine and an expensive pile of scrap metal Here's how to check clearance using clay.
The relationship between the valves and the pistons is a precarious one. Too little space and they collide; an occurrence which results in carnage that, at the minimum, requires replacing the valve(s), guide(s), and piston(s). At a maximum, it necessitates a complete engine rebuild. Nobody wants to pick chunks of steel and aluminum out of an oil pan.
Piston-to-valve clearance criticality is exacerbated by high-compression pistons, large-duration cams, and high rpm. For these reasons, it’s imperative to check piston-to-valve clearance whenever an engine is built, or either the cylinder heads or valvetrain are changed. Checking this all-important clearance is not difficult and can pay huge dividends in durability. The shortest route to disaster is assuming everything is OK.
In order to check clearance, you will need Play Doh, or similar modeling clay, an inexpensive dial caliper and a pair of solid lifters. As for the engine itself, the short block needs to be finish-assembled, you’ll need the cylinder heads, head gaskets, and the camshaft/valvetrain that will be used. The process, as detailed in this article, is simple enough and could mean the difference between a happy motor and a sad wallet.