Sealing header joints - ideas?

[Yamma-Fox 403]

I am formulating my plan for fabricating a header for my Yamaha but no matter which way I look at doing it I see a need to make gaskets and likely use some soft type compound to fill small gaps since I assume I will have a bit of warping after welding.

My "A" plan right now also includes slip joints that will need some flexible material to seal them up a bit as well.

In snowmos I have simply used the highest temperature rtv to stop header leaks and even build temporary gaskets on the trail.  It held up well even though it is listed for only 700 deg F.

I assume there is a better product.

 

 

Edited 5 Apr 2018 by Yamma-Fox
Retitled to describe better what I'm looking for help with

[Av8r3400 1178]

Does the header have one continuous flange plate or four individual ones?

Either way it could be cut in a machining center, surface ground or even flat sanded after welding to make it perfectly flat.

 

[Yamma-Fox 403]

Yeah My plan right now is to build off the head with individual flange plates welded to 45 deg bent tubes (1.5" aluminized steel).  Each of those will connect to a Yamaha R-1 titanium motorcycle header which has a 4 to 1 collector with a 3 inch outlet.

So my joints are:

At the head / exhaust flange where I plan to use a thick "crush to seal" type automotive gasket:

https://m.ebay.com/itm/Percys-High-Performance-66033-Exhaust-Gasket-Seal-4-good-Ford-2-valve-Round-4-6/182331761487?hash=item2a73d1e34f:g:DhYAAOSw~xlaq8yA

The next joint (4 of them) is the 45 deg bent pipes to motorcycle header where I hope to fit some 1.5" donut type gaskets.  I plan to fit those by sleeving the 1.5 into the header a short bit and spring fitting them together to allow a little wiggle and expansion room. 

The remaining joints are from the header outlet to the muffler and post muffler to a 90 deg outlet out the cowl.

With all of those joints I think I'll find some with small leaks at am looking for a "rtv like" soft gasket material to help seal things up tight.

Just not sure what product would be best...