Subject: Re: Unleaded Conversion...
Having had 2 engines done, as good a reason as any is to return the head, seats, valves, springs, colletts, guides, tappets etc returned to new condition and clearances using more modern materials as necessary than were available when the head assembly was designed in 1957-58. Unleaded also burns hotter than 4-star so attention should also be paid to all aspects of cooling, especially in the head around the exhaust valve guides which are cooled directly by the water flow, and in general around cylinders 5 and 6 where flow is reportedly weaker than elsewhere