Cleaning and lapping

There was quite a thick layer of carbon on the valve faces which was very hard to clean up without removing the valves. I also realized it's probably best to reseat them too so I removed them once again.

On the left there's the one that I cleaned valves in place and how they looked like before. The intake valves got pretty shiny but the exhaust valves still are a bit dark. The surface is smooth and all the carbon is removed but didn't manage to polish those as well as the ones in the other head. So I removed them from the heads, attached to a drill with a piece of plastic tube to protect the valve and run them against a scotch brite pad lubricated with WD-40. On the right side you can see the results: Both intake and exhaust valves are bright and shiny but it didn't come easy, specially for exhaust valves. I probably spent half an hour for exhaust valves to get the carbon off while intakes started to shine in half of that time. Well, they are clean now even though the same treatment didn't make exhausts very bright on the other head. They are clean and carbonless still.

For reseating I used fine valve grinding paste and a manual tool. The contact surfaces had some carbon dots on those but they disappeared in the process. I ran a brief leakage test by pouring some alcohol on the head and visually inspecting the intake and exhaust channels and saw only one very small leakage on vertical exhaust valve. I think it took 10 minutes to show up but since the valves were still unattached to the rocker arms it was easy to just reseat once again. I ended up using coarse grinding paste this time first and then some fine again and I think I got it seated so the leak was finally gone.