Hello,

I take it you meant the head is not yet installed on the engine but had gone thru the milling process.

I haven't heard of any such way to clean the valve without taking it out (when the head is already out).

The usual way is to put in the plugs, flip the head over and fill those combustion chambers with gasoline. See if any leaks. If there is follow up with grinding the valve's mating surface with grinding paste. Repeat process till there's no more leak.

You then measure the gasoline volume from each chamber to ensure equal volume distribution.

Hope this helps,
Amarin.