I make sand bent headers for vintage race cars out of mild steel tube. The routine is to fill the tube with tightly packed sand, heat to dull - medium red and bend by hand. I use a no 8 rosebud tip and O/A. I am looking at trying to do the same with stainless tubing, most commonly 1.5" to 2.5" 16 ga 304 seamed tubing. What I'm not sure of is if stainless has similar plastic properties to mild steel under that sort of heat, and what colour it goes?
Thanks, Brian
Hi Brian, I too make headers and sheet metal intakes for professional drag racing. I have not had any instance of using casting sand other than as a heat-sink so far but I asked one of my welders about this and she informed me that the SS tubing will require more heat to gain the same plastic properties and that the material will take a grey then cherry red change rather quickly. The tubing can be bent without kinking when it is the flat gray That is the ideal heat I'm hearing from her. Once it goes cherry red it will pull off weird angles, kink and or buckle on tight turns (i.e.: a flange plate) Working with it red she turns down the heat a bit and then bends on a jig or free-hand. I never had any issues myself but I have been lucky enough not to have issues other than the SS turning "gold and blue" on the weld seams. I can send you all the AWS stuff I have if it helps you but from what I'm told and from my own experience it's no different than traditional metals for exhaust. Other than the final discoloration there is no difference whatsoever we are aware of. I tried Ti. for a twin turbo setup on a 640cid BBC and I ruined two tubes as I suck at Ti. welding so far. Wendy did all the work in a old sand-blaster cabinet I turned into an inert welding vessel. Hers are perfect on all accounts. and it looks awesome all together but again, the joints are discolored but who cares! In my realm prettying up parts is not a big issue for the die-hard racer. My client base with show cars and custom work makes me want to tear out my hair most of the time. I have a plating company that is killing me on cost however. As a side note I Jet-coat most of the parts for thermal relief of fuel charges, and it pretty much looks bitchen and holds up great except for about 10" around any turbo or outlet.
let me know if you need more,
Rob Fraser
Fraser Competition Engines Chicago, IL.
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