I shall be changing the cylinder head on a friend's 300 tdi this weekend. He bought a new head but we shall be swapping valves, injectors, etc over. The valves were very recently re-cut and lapped in and the engine has only run for a couple of hours (the head turned out to be cracked internally, hence filling and skimming was a waste of time and money). Do we need to re-lap the valves when fitting them to the new head?
Job done. Slight lapping with fine paste, cleaned everything up thoroughly, new head slapped on and all's fine 
I was a bit concerned with the amount of soot I found on the pistons and valves (considering that everything had been cleaned up a few days earlier and the engine only ran for 2 hours or so). Fuelling and turbo-boost have been tweaked so that might be the culprit but I think it's was excessive soot.
I was a bit concerned with the amount of soot I found on the pistons and valves (considering that everything had been cleaned up a few days earlier and the engine only ran for 2 hours or so). Fuelling and turbo-boost have been tweaked so that might be the culprit but I think it's was excessive soot.
