Originally Posted by oldbogie
I'm not to sure that lapping if that's all you did will be adaquate, especially if this is a heavy duty or an emissions head with hardended seats.
So that leads me to the question as to whether you used a seat cutter/ grinder before lapping? Lapping alone as a seat restoration process makes the seats too wide and the valve ends up not settling well on the seat. Also, did you restore/replace the guides. When these get loose the valve rather orbits the seat having a hard time setting itself down.
I just lapped them to clean up the grime, the engine sat down for several years, the seats and valves are ok, not worn, so are the guides, they didn't need a restoration, the engine has low millage, they are not too wide now, I lapped them not to correct any problem, just a clean up job.