Okay, what do we use for the preheater?

I find that 1/8 inch K & S copper tubing will work if you anneal it first. The trouble is it's hard to bend to small diameters, for example, around the exhaust tube of a 4 stroker, before the muffler.

The next smaller size, 3/32, is too constricted, and doesn't permit sufficient flow. Tough to construct headers or junctions for multiple 3/32 tubes.

Does anyone have a source for good preheater coil tube?

Does anyone drill holes in their 4 stroke mufflers and run in the smoke tubing?