[malc9141]

Thanks for reply. Welcome, as usual.

I still doubt if the rail pressure is being opposed by the valve. It is enormous, for example if you had 0.5 sq mm area to oppose at 1500 bar, you'd need about 110 kg wt to shift it. Why do that, if you have the lead in of the pressure at the side of the piston-valve, which gives zero net force?

But I'll look at your other suggestions and keep at it.

Malc

PS
It's so funny, I took the cylinder head to experts last Sept. "Don't let a machine shop do it, we'll do it." Nothing happens. Try elsewhere. Exactly the same. Another 12 weeks. Now, a third guy. He says, "Is this the only one you've got?" meaning "Is it Ok if I wreck it?" He also says I've been grossly over-charged by expert No1 for valve guides - which I'd wondered about.
I have to get that back and get my Machine Shop to do it!!

Also, I paid ~£250 for a rare starter motor and starter ring gear, and yesterday, EXACTLY what I'd needed was on eBay for a bid of £40. Oh, it's cruel world.