Install Seats and Guides
Proper seat and guide installation is so critical that we have a department set up for just that!
If a guide is not put in straight it can cause the rocker arm to contact the valve tip on one side before the other. This can cause the rocker arm and the valve tip to fail prematurely.
If the guide is not installed with enough interference, the guide can become loose causing catastrophic engine failure. Also the conduction of heat from the guide to the head helps cool the guide, so it is important that the guide be installed in a smooth hole.
If a seat is not installed with enough interference it to can become loose causing catastrophic failure. The seat also depends on heat conduction to cool the seat which in turn cools the valve while it is closed.