I have been having problems with a 1600 xflow, It came in a project car, it would start and smoke very bad, filling garage with smoke and running badly, I had relapped the valves a few years back and fitted all back together, it appeared to be ok but has a noisy camshaft. So I have just taken off the head to check, bore number 3 is clean, the others look normal. Any ideas, compression test was a lower on three, had spark on all four plugs. Why would this cylinder be clean compared to the others? 😕