Thanks Paul, now balanced (I hope ) and No 4 responding much better to tuning Rob - My tubes are F16, I havent pushed the engine yet but there is a bit of a pick up issue at low revs but once passed 2500 it flies but I haven't yet been above 5500 & rev limits at 7700. The head & pistons etc have been modified by Dunnell and I now have there hi spec cams, reputedly 210bhp I have found a set of F4's so I will give them a go I seem to have a problem with filters, the engine runs like a dog with the spongy socks, but once off it is fine, the K&N's dont quite fit the bonnet although they also work fine, currently running with gauze across each intake Nick