PT: Exhaust Pipe Flange
- Thread starter erik
- Start date
Hi Erik, I seem to remember Clev Trev suggesting the use of a big end spacer ring. Cheers, Stu.
Erik, if there is any doubt that the flange on the pipe is exactly at 90 degrees to the pipe and that the original type of sealing washer will not seal the gap exactly it is possible to use clear silicon mastic which seems to withstand the heat. It also does not set solid so that it is always possible to remove the nut afterwards. I discovered this years ago when passengering on a racing sidecar outfit. Many sidecar racers work on a very tight budget and in the lunch break two of the chaps had their cylinder head off and were reinstalling it with the aid of domestic silicon sealer. They claimed it lasted for ages. Since then I have tried it myself, not as a cylinder head sealer. and it works. The reason I say 'clear' is that from my experience sealing hatches on sailing boats in the Med if one use clear it last for years, any silicon with a pigment in it fails after about one year.
I think I will use some glas fiber wrapped around the pipe into the head recess. So alignment is not a factor and not a problem when taking off the pipe later. Look into some glas fiber chimney seals or these ridiculous ex pipe wraps and use some of it for sealing .
Vic
glas fiber
Vic
glas fiber
The big-end spacer ring has worked for me in the past, but I have had to build so many exhaust systems that I wanted to do something a bit more reliable.
I bought a form for making the 45-degree bend. Once it is at 45 degrees it is easy to press it flat on a plate. I made a tool to hold the pipe stub in the press and I made it so I could grab the tool in a lathe.
I used 1-5/8 ID pipe, split the top, and welded on flanges so I could tighten up the pipe. I used the spacer at the right at the bottom of the tool to shorten the overall length or vary it if necessary. A two-inch length seems to work. The bending is straightforward
I finish the bend on a flat plate.
I use the lathe to trim the outer edge of the pipe to the correct size.
We have been using these for several years on David Tompkins' racer. These are stainless steel.
David
I have a block of alloy with a hole in the centre split in the middle I have a 19th century big vice I grip the pipe in the block heat it to cherry red and simply knock over a flange with a hammer quick touch on my linisher to flatten face make sure edge is round to fit job done.
I do have one head with a alloy stub welded on the exhaust port its supposed to be inefficient heat wise but it sure was fast to fit a pipe!
I do have one head with a alloy stub welded on the exhaust port its supposed to be inefficient heat wise but it sure was fast to fit a pipe!
When I did mine I originally did the flange square to the end of the pipe (A) but as the pipe is curved and the nut is not then the exhaust exits the nut not in the middle and the rest of the pipe did not line up with the brackets that well. When I redid it at a slight angle (B) so the exhaust exited the nut centrally the rest of the pipe lined up nicely with the fixing points and it looks better where it exits the nut.
A small angle at the head will make quite a difference so you would have to make sure that the pipe fits the bike if this is done.
The hole will be very slightly elliptical but not enough to matter. I think the important thing for good sealing is to make the flange well in one plane - I used a hammer so not perfect but the sealing washer copes.
A small angle at the head will make quite a difference so you would have to make sure that the pipe fits the bike if this is done.
The hole will be very slightly elliptical but not enough to matter. I think the important thing for good sealing is to make the flange well in one plane - I used a hammer so not perfect but the sealing washer copes.
That is a perfectly good way to do it. I prefer to bolt the stub in place and weld it onto the next part of the pipe, be it one piece or ten pieces. On the racers, the radius is often very tight and there is a lot of shape very quickly. I like to keep all the cuts on the centerline of the tubing. This way there are no gaps and I can do autogenous welding (without filler rod) which seems to work well, so far.
The clamps allow me to tack the pipe up and build it as I go.
David
The clamps allow me to tack the pipe up and build it as I go.
David
Machine on a Lathe (preferably a Schaublin, but can be any...that Stephan has) a Stainless flange, with about 8-10 mm "pipe" on it, and grind the exh. pipe very perpendiculair to it, (have an "half open" old nut) TIG weld, and it fits always very well!! no hammering on bend pipes etc. as thats always on the piss, hence stripped threads. you know...