Valve Guide question
 

How do i know when to oversize valve guides? I have the standard ones with 100k on them and the valves have a bit of play in them. Should I just get new standard ones or do I need to oversize? This is an M103 motor.

Measure the valves -- if they are undersized, get undersized guides if you want to keep them. Usually, on MB engines, you are best off to just replace with standard guides. The valve stems normally don't wear much.

Do take a look at the valves themselves, though. If they will be near the wear limit when ground, get new ones, they aren't that expensive.

Peter