Bob.Murphy wrote:Changing to Mk II guides might be an answer (if they fit - I didn't do this and don't know the respective dimensions). Alternatively, getting new guides turned-up with a top that allows the rubber 'valve guide seals' that one gets in car engines to be fitted would be a better option.
MKII guides don't fit! I installed new guides on mine but Drags sent me the wrong ones for the MkII by mistake. I only noticed after having the engine assembled that something was wrong, as I couldn't turn the camshaft a full rotation. The valve collars were hitting the top of the guides, so the valves wouldn't open fully and blocking the movement of the rockers/pushrods. I had to disassemble the head and mill the top of the guides down to the MKI dimensions.... I have a thread on here with all my head scratching questions at the time.