Thanks guys,
That has given me a lot to think about. The engine itself is less than 3000 miles old, still brand new. The cooling system is close to 100%, my only problem is that I don't have those sealing rings that seal up behind the spark plug, I'm getting a new set of HT leds which will have them. Forgive my lack of lingo, but what does WOT stand for? I have retarded my ignition to about 3 degrees btdc, as I have a single vacuum dual advance dizzy, this has helped. But my only problem is that the fuel I'm running is the highest octane available in my country, it's 97 (I think RON), I might try an octane booster additive, could those help?
I also suspect a higher than normal compression, the guy who built it said the heads (originally 1300) had been opened up, but never said by how much. As for the carbon build up, is there any way to clear it away within a strip down? Could correcting mixture and going for a long trip free the carbon up?
Thanks Regards Kevin