lapping valves to check seating

[Dragsinger]

do you lap the final valve job, or, for a double check of seating is doing so acceptable?

[Mike Taylor 3601]

The tool for checking seats is concentricy gauge but Lapping will tell you alot,but vaccumn test for seal is better,if you pass those,and want to test farther install heads (no rockers) and hook shop air @ full press mine is 160,cover port with hand if can't feel it build any pressure then it's sealed.
I have found valve problems this way that,compression test,leak down test, would not show anything wrong,but air test showed,the problem.

It's old school but we still lap every valve job we do. it's not a 100% but if it won't lap in it sure won't seal, but on the other hand it can have nice ring on valve and seat and may not seal 100%,the finer the compound is the more precise the valve job will have to be to leave ring on valve and seat.
Mike Taylor 3601