So last summer I had the XK120 on rolling road and set up by a guy who knows his stuff here in the UK, so no issues there. Now the #6 plug (the one nearest the firewall) fouls up after 20 miles or so; so badly that the car mis-fires / runs on 5 only. The other plugs are fine color wise.
Early 2018 the engine had a rebuild and there has has been a bit of valve noise and was agreed that would let car settle in for a bit before adjusting. So would an “off” valve clearance be enough to allow 1 cylinder to run extra rich ? Or should I be looking for something else too / instead off ?
Collecting expertise and thoughts before collecting spanners