A difference of 3mm - hmm that doesn't sound too great.

I've checked some specifications for you. The valves on the turbo OM617 should be 131.5mm long => same for either the intake or the exhaust valves.

What you could do is put the piston to the top of the bore and remove the valve springs for both valves. So long as the piston is at the top of the stroke the valves won't fall in. You could then measure the heights of the valves again to see if it is a valve seat problem or not. Whilst you're at it you could then compare the condition of the two rotocaps...

I'm hoping for you it is a rotocap - nice easy fix if it is!

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!