Alex:

Don't worry about valve timing. No neeed to disturb the cam for a top end cleaning. And if you can do the head on a 2s with no problem, it's just the same on a 4s regarding the mounting of the head, if you don't loosen the valve adjusters and put everything back in the original position you might not even have to reset the valves.

One thing. DO NOT use any lapping compound on the valves or seats - after you get the deposits off chuck the valves in your electric drill and lightly polish the seating face with a pencil eraser. Spin the same pencil eraser on the valve seats to clean them, then put it all back together.

Bill.