My primary runners are 0.049 6063 T832 Drawn  alum 1 .25” in diameter.  My secondary runners are of the same tubing but 1.5” in diameter.  Below is best source for this Drawn aluminum tubing that I found.

 

http://www.texastowers.com/aluminum_.htm

 

 

In my case I wanted them adjustable by having the top half made of larger tubing – in fact I got the special aluminum tubing used for telescoping antenna elements so the bottom and top would slide together smoothly.   If you don’t plan to do that then 6061 T6 will work just fine.

 

I cut off the heavy cast aluminum tubing of an 86 N/A upper manifold, milled a shallow recess around the air hole, set the thin lightweight tubing down in it and brazed it with HTS-2000 (the only aluminum brazing rod I’ve ever had any success with).  You could possibly tig weld it – but I had somebody try with a Mig welder and the thin tube and heavy casting (manifold), just didn’t come out well.

 

http://www.aluminumrepair.com/

 

 

Hope this was helpful

 

Ed

 

 

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