Valve lift and plug clearances

[RobThomas]

Any ideas how high the valve ever gets into the head? It just occured to me that the heads have been skimmed a lot over the years and the tip of the plug electrode must be quite close to the valve, even when new.
Any experience of this? Anyone got an engine on the bench and able to measure the height of the valve at max lift?

Cheers

[mike.perry]

Inlets 0.256in, exhaust 0.260in
You have to make sure that you use short nose plugs or else they will be hit by the valve. Ask me how I know!

[RobThomas]

Thanks, Mike. The Derrington has 3/4 length plug holes so I assumed it needed them for heat removal. The plugs sit with just theelectrode arm sticking out and the threads flush with the bottom of the hole (ideal) so I assume the L10s (1/2 inch ) sit in shallower holes?

Keith?

[mike.perry]

I had not noticed any difference in the depth of the plug threads, they look the same in the photo. Not questioning you Rob but is your head the same Keith?
You never know, we might find out that they used two different plugs