Header fabrication

[CALfeRacer]

I'm planning on building a new exhaust for my 250, from the headers down. I have a plan for making the 2-1 collector, calculated my ideal header length and diameter (thanks to Sonreir and his "doing it right" thread!) and am almost set on what I want to do as far as muffler choice. My only question is the best way to go about making the part of the header that connects to the engine block. The header has a greater diameter at the very beginning, which the collars grab, and all of it is pushed down by the flanges to get a nice seal (circled in red in the pic). My question is how to replicate this design without chopping up the old pipes and welding them on to my new ones. This is because I'm changing the OD, and I want to sell the pipes to someone who needs them. Also would be a nice way for me to pay for the new exhaust . I figure it could be done with a thicker piece of pipe welded on to the end and cleaned up, but was wondering if anyone knew of a better way to do it.
Thanks for any help, and I'll be sure to post up everything I do once the time comes where I can use the school's welding equipment (hopefully in the next month or two?)

 

[SONICJK]

You've got it that's pretty much the easiest way to do it.
Get a larger pipe that fits over the smaller tightly and that the collar will grab.
Weld it on the engine side and grind your welds back nicely so it still seals against the gasket and you're good to go.

 

[CALfeRacer]

You've got it that's pretty much the easiest way to do it.
Get a larger pipe that fits over the smaller tightly and that the collar will grab.
Weld it on the engine side and grind your welds back nicely so it still seals against the gasket and you're good to go.

Awesome, sounds good. Thanks!
Like I said earlier, I'll try to remember to post up pics and such either on this thread or a new one. Problem is I need to get about 5 more hours in the shop to be allowed to use the welding equipment. Seems crazy to me that you can't just get permission if you take a welding class (which I am doing right now). Speaking of, should I be using TIG or MIG if I'm welding mild steel pipe?

 

[SONICJK]

I tig everything.
Either will work, tig will make a much prettier weld that you shouldn't have to grin back.

 

[CALfeRacer]

I tig everything.
Either will work, tig will make a much prettier weld that you shouldn't have to grin back.

I will keep that in mind! I get to do TIG this week in welding, so I guess I can decide which I like more after that! Right now I'm a pretty big fan of MIG, but I guess that's only compared to stick welding... wasn't a big fan of stick welding.
I'm not terribly concerned about how the weld looks, as I'll probably be wrapping or painting the pipes. I wrapped my 125 pipe with the titanium wrap and I was a fan.

 

[cqyqte]

Honestly, I would go to your MetalSuperMarket and buy a length of mild steel tube with the correct outer diameter of the header piece with a wall thickness that you can machine the proper inner diameter. Then take the tube to a local machine shop and have them machine two pieces for you. The flanges will be similar to these which I made from this drawing provided by a member on a CB450 Forum...

Now your dimensions will be different I suspect but the concept will be the same. The inner diameter should match the exhaust port diameter as well the inset diameter should match the outer diameter of your header pipe which you plan to build your 2 into 1 pipes from. Once you have these flanges built you will simply ring weld them onto your completed exhaust system.

Do it right and you will be happier with the end result.