Aaah - seriously kicking myself right now!
So, checked the valve clearances just now. All ok, number 1 is a bit closed up mind. Loosened lock nut, adjusted, seemed ok. At this point I get distracted by a phone call. On returning, I forget about the lock nut and, thinking I've finished the job, spin the engine on the starter. Clunk. Oh sh*t!
The exhaust valve on 1 is fully at the top and the engine won't turn by hand after a certain point. Removing the spark plug I can see the piston moving up and down, but there's a point (roughly 45 degrees after TDC) when it won't move. Now horrible feeling that I've just managed to cause a piston to hit a valve with all the mess that entails.
The irony is this was the last check I was doing after having done the rest of the servicing and everything was running beautifully. Currently kicking myself!
Any Pinto experts in the North London area who would be willing to pop to N19 to give their opinion...?