After removing the head, the condition of the valves appeared fine. I turned the camshaft over a few times whilst on the bench and still fitted to the head. There didn't appear to be any sticking valves and things seemed OK. I re measured the clearances. One of the exhaust valves was a little tight, this I altered and refitted..
I agree with your comments it certainly to me in any case, sounds very much like a timing problem.
I have a cooling leak to fix on the heater box behind the head and will then carry out a timing check as follows, hoping that this invites comment..
Loosen the distributor slightly so that it can be turned by hand The vacuum pipe still attached
First I will start the engine (hopefully) on choke, am not sure what the revs will be , they could be anywhere.
Allow the engine to warm through, remove the choke and again hopefully the engine will settle at less than a thousand revs.
Attach the strobe to number one cylinder near the radiator
The pulley at the front of the engine has been marked with white paint at 6 degrees before TDC as has the pointer on the front housing.
Set up the timing as close as I can possibly get to 6BTDC and retighten the distributor.