MO 35-pt no 506....?

[Albervin]

Hmmm, I have a '48 B with 3 piece pipes. The front exhaust nut does not screw in a lot but enough to keep all the gases in. I recently had an experience with a silencer for my "A". It was sent back 3 times due to
"errors". Now it looks good AND fits but is way too loud. Not a lot I can do about that either, is there? I agree that if the pipes don't fit with a small amount of tinkering they should be sent back (at the supplier's cost).
To expect us to cut and flange the pipes is bit much to ask when just checking the tappet clearance is a major accomplishment .. For some Vincent owners here in Australia the nearest real help can be over 300 miles (500 Km) away and I would reckon we are not unique. It is accepted that the bikes were hand made originally but when exhausts made with the original tooling are impossible to fit then something needs to be done. As far as the units made by Overland here in Australia it is a lottery BUT the freight is cheap and so are the phone calls!
I would limit the number of gaskets to 2. I knew someone who obtained a perfect fit with 3 but then a leak developed. Guess what he found? NO gaskets........

 

[Hugo Myatt]

At one time it was fashionable to fit Norton exhaust gasgets. Can't remember which model. These were copper asbestos which at least had the virtue of being squashy.

 

[stumpy lord]

Available from vin parts and probably from club spares as well.
stumpy lord

 

[fgth130]

Here's some background to the exhaust pipes issue. The works had a dummy set up of 'rejected as unacceptable' crankcases, barrels and heads for checking the fit of the pipes; later on, when prices skyrocketed this collection became too valuable and was eventually sold, result nothing to check against.
Also, the original pipe thickness was specified as 20 SWG (0.036" thick); this became commercially unavailable (anyone own a steel mill?) and the nearest you can get is 18 SWG (0.048" thick). This doesn't appear much, but it's a third thicker, and it makes the pipe bender's problems more difficult. Put the above together and it gets tricky.
Frank Griffin

 

[timetraveller]

A few years ago I was at a Boat Show and saw a pipe bending machine being demonstrated. It was programmable and consisted of several sets of rollers which could be moved, under computer control, to move either horizontally or vertically. A ram pushed the tube to be formed through the rollers and movement of the roller could impart various curves. For demonstration purposes the guys were extruding a 50 mm diameter stainless steel pipe which as it emerged took on a series of almost right angled curves. I am a great fan of Bob Culver and his determination to keep on producing spares for our bikes but modern equipment could produce what we want, accurate every time, to within thous. Certainly the program would have to be worked out until we had a set of master pipes which were correct but after that it should be easy and cheap. On one occasion I took a new Vincent owner back to Bob's to challenge him to fit a set of his pipes to the new owner's engine. They would not fit and Bob was of the opinion that it was a 'build up of manufacturing tolerances on the engine'. I then slackened off all the head holding down nuts so that both heads would move on their respective studs. Total movement is thous! My opinion is that it is the pipes which vary and these days the technology exists to get pipes made accurately.

 

[Bill Thomas]

If you watch, Freeview in uk at 8 pm most nights chanel 38 you will see this tool used, Cheers Bill.

 

[vibrac]

"but modern equipment could produce what we want, accurate every time, to within thous."
Yes but every Vincent is different A. has packing under the cylinder B. has some cast exhaust nuts ,D has a crankcase face that needed a extra pass back in 1951.... etc etc
Its no good applying a lazer cut breast plates to a hand beaten suit of armour. A much better idea would be to produce a range of pipes all slightly different so that we could bespoke fit them... hang on, isnt that what we have already ?

 

[timetraveller]

I do not disagree with what you say but if we are only talking about the heads moving up and down by perhaps plus/minus a sixteenth of an inch then I guess that there is enough flex in the pipes and the joint where the short rear fits to the long front pipe to take care of that. What I have experience of is pipes where, when the rear pipe is fitted, the front pipe is half to three quarters of an inch to one side of the front port. Also pipes, that when both pipes are fitted, the end of the silencer is about two to three inches too high. Shortening the front one where it goes into the port can take care of some of that but then one finds that the rear pipe does not fit. I’m not sure why cast or machined nuts should make any difference. I have used both, even mixing and matching and never found that that is where the problem is although sometimes it has been necessary to relieve the inside of some nuts to allow the pipe to take up the correct line.