Cast iron 1-piece exhaust / inlet manifold balance tube braze or ?

Hi
　
Have a newly cast iron manifold , its for an inline 6 cylinder flathead
it's a combined one-piece exhaust + inlet manifold with twin carbs

All the appropriate surfaces have been machined.

There needs to be a light wall balance metal tube approx 3/4" diameter ,12" long attached between the inlet parts.

What is the best means of fixing the tube (probably stainless) in place ?

Don't want airleaks ,also due to the exhaust manifold being integral some heat will get to it .

Brazing with brass rod ? Silver solder ? High temp epoxy adhesive ?

Any precautions ?

　
Thanks in advance for any advice.

 

Pipe thread + fittings + copper tube ?

 

If you can make it work, I would use threaded fittings. If that's not an option, the best possible solution is heating the part red in a furnace then gas welding with iron rod and appropriate flux, creating some bosses to later drill and thread into. Even if the manifold is clamped to a flat plate, welding it that way will most likely require re-machining flat. TIG welding with special rod usually doesn't work out for what you are wanting to do. Brazing is a roll of the dice. Some parts braze well, others can't be brazed at all. The durability of the brazed party is also a roll of the dice. Sometimes things work out, other times not. Brazing can be done with a TIG torch and special braze alloy, or it can be done the traditional way with a gas torch. If you are going to try TIG welding , TIG brazing, or torch brazing, preheating the entire part will inprove the chances of a good outcome.

 

Thanks for those opinions.

It's a restoration application & is somewhat visible ,so didn't really like the idea of the fittings although it is a good one.

It's a new casting & there is enough thickness of cast iron for threads .

As it was tricky to hold for the machinist to machine the surfaces ,not really keen on the risk of distortion with a good deal of heat !

Probably originally the balance tube was brazed? in place & then the machining done.

It will be getting a ceramic coating , jet hot or similar , I wonder if they have any "sealing" properties ? (If had tube a tight push fit in the holes )


Maybe will end up using threaded fittings / olives / copper tube & then getting the whole assembly ceramic coated ...