Lapping The Valves

Lapping the valves should not be absolutely necessary after a valve job but I did it anyway to see where the valves contacted the seats. The heads had been modified quite extensively so I did not want leave any doubts about the valves fitting them.

Lapping itself is really simple. I bought some lapping compound and a lapping tool that is just a stick with suction cups in each end. The grinding compound had coarse and fine paste and you start with the rough stuff. I spread it on the valve face, pushed the stem in the guide and attached the tool.

I rotated the lapping tool back and forth between my hands while pressing it lightly towards the head. After a few rotations I tapped the valve with its seat a few times to get more paste between them. After doing this I got a nice grey ring on both surfaces. Then I needed to clean the valve and seat and do the same thing with the fine paste. It took a few hours to lap all 16 valves.

All seats were fine but the contact area on the intake valves was quite near the edge. Should be fine but there is no room for any more machining.