Going back a few threads when various adjustments with regards to the positioning of the heads and thus the exhaust port threads was being discussed; several years ago I was helping a chum, new to Vincents, who was having trouble fitting his brand new “official” twin exhaust pipes. I went over to help and there was no way that I could make them fit so we put the engine in the back of his car and took that and the exhaust pipes back to the manufacturer and challenged him to fit them. He tried and failed and then said that the thought that it must be a build-up of manufacturing tolerances. So we slackened off the head nut and everything else that needed to be slack to allow the heads to be rotated etc. and there was still no way that the pipes could be fitted. The thing to note is that there is almost NO movement possible, certainly not tenths of an inch. Clevtrev’s point about original machining tolerances, exhaust port thread repairs, distortion of the heads after sixty years of use is well made but when pipes do not fit within a half inch to a full inch then it is going to be the pipes, not the engine. It would be good to have David Bowen’s feedback on this as to whether this was a problem during manufacture. My understanding is that the bikes were road tested with each tester using his own set of exhaust pipes and then changing them for new ones prior to the bikes being shipped out to the dealers or customers. This suggests to me that there could not have been a serious problem at the time.
I am using a very unreliable internet connection at the moment and lost the whole of the first version of the earlier (and this) communication. What I had put in the earlier posting, but which was left out of the second version, was that more recently I have heard of people buying Armour pipes which did fit so it is possible that their quality control has now improved. Feedback would be good.