stripped my engine ... measures valves with a straight edge ... outer valves on both heads seem 0.5 mm higher ? (these are the exhaust ones, see photo below) is that enough to indicate seats have dropped and I should get a new head / refurb this one ? rest of the engine looked pretty good, followers, pistons etc .. suggesting the 78 k on the clock is original ?
I would say you're stressing over nothing dude... no seat regression going on there... a dropped seat is where the seat comes out and jams the valve open allowing the piston to hit the valve... I'll go find a pic of a regressed seat
here you go have the valve/tappet gaps been nipping up? if they have it could be the valve stems stretching...
Thanks ... I guess I didn't mean dropped as in dropped out ... ! Not sure about valve gaps as I have no history bus is US bought for rebuild ....
well, if they'd dropped (came out slightly) the exhaust valve stems would be shorter than the inlets, not longer...
These heads do suffer from valve seat regression when they've been run hot though. If it starts running lumpy and you find a gap(s) closed up, reset it then see how far it is before it runs lumpy again. If its just a few hundred miles you'll get sick of resetting it before it drops right out. That's my personal experience anyway. Most times I also find a leak in the brake servo vacuum line somewhere that's caused it to run lean.
