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What matters for stainless exhaust headers

Header tubing is usually thin enough that a capable TIG welder is less important than steady low-amp control, a torch that fits tight joints, and good gas coverage. Most automotive stainless header tubing is roughly 16–18 gauge, about 0.048–0.060 inch thick. At that thickness, a little too much heat can open a hole or pull a flange out of alignment. A machine with a 200-amp maximum output is ample; the useful feature is a stable arc at low current, not a huge top-end rating.

For most work, choose an inverter TIG welder with DC output, high-frequency start, foot-pedal control, and adjustable post-flow. Stainless headers do not need AC unless you also plan to weld aluminum. Pulse is useful for controlling heat on long seams, but it is not a substitute for fit-up or torch control. If you are comparing basic machines, a DC TIG welder with a foot pedal and high-frequency start is the practical starting point.

TIG welder types compared

For repeated fabrication, avoid buying on amperage claims alone. Check whether the machine includes a usable pedal, the torch connection is compatible with common consumables, and the duty cycle is stated at a realistic output. Header work often involves short welds and repositioning, so a moderate duty cycle may be adequate. A machine rated for 200 amps at a low duty cycle can still do this job, but it may need cooling breaks during longer fabrication sessions.

Features worth paying for

High-frequency start makes an arc without touching the tungsten to the work. That matters on stainless: a touched tungsten can leave inclusions in the weld, and the contaminated tip needs to be re-ground before continuing. A pedal lets you reduce current as the joint heats up or as you close the final gap. If you prefer torch controls, confirm that the welder and torch actually support them; many entry-level machines do not.

Adjustable post-flow keeps shielding gas over the hot tungsten after you release the pedal. Roughly 5–10 seconds is a useful starting range, adjusted for current and tungsten size. Pre-flow helps protect the start of the weld, while pulse can alternate between higher and lower current to limit heat input. Neither feature fixes a poor joint: a header tube with a gap much over about 1/16 inch is likely to sag, burn through, or demand excessive filler.

AC/DC is worth the premium if aluminum is also on your work list. For stainless headers alone, DC TIG is the sensible buy. If TIG is only needed for occasional tack-ups or small repairs, a lower-cost lift-start machine can work, but expect less control and spend more time managing starts.

Gas, filler, and consumables

Use pure argon for TIG shielding, typically around 15–20 cubic feet per hour in still shop conditions. Too little flow can expose the weld to air; too much can create turbulence that pulls air into the shield. A small gas lens improves coverage and helps when the torch must reach around bends. Consider a TIG gas-lens kit if your torch supports the parts.

Match filler to the tubing alloy and service conditions. ER308L is commonly used with 304 stainless, while ER316L is appropriate for 316; verify the base metal before choosing. Use filler around 0.045–1/16 inch for thin tubing, depending on joint fit and technique. Keep filler rod clean and dry. A dedicated stainless wire brush and clean cutting tools help prevent carbon-steel contamination, which can lead to rust spots around the weld.

For exhaust work, the inside of the tube matters too. Back-purging with argon reduces heavy oxidation, or “sugaring,” on the root. Sugared welds are rough and can create a restriction or shed scale. Purge flow can be low—often just a few cubic feet per hour—because excessive flow wastes gas and can disturb the weld pool. Seal the tube ends, leave a small vent, and confirm the purge has displaced the air before welding.

Fit-up, heat control, and common failures

Clean the joint to bright metal, remove burrs, and tack the tubes in several places before welding the full circumference. A practical starting range on 16–18 gauge stainless is roughly 35–70 amps, adjusted for joint geometry, machine behavior, and travel speed. Begin lower and use the pedal to add current as needed. There is no single setting that works for every tube: a tight butt joint takes less heat than a thick flange or a joint with a gap.

Short, controlled weld segments and alternating sides help limit distortion. Let the assembly cool between sections rather than forcing a continuous bead around a hot tube. Common problems include burn-through from lingering at the puddle, a pinhole caused by poor fit-up or contamination, and a rusty or dark weld from inadequate shielding. If the puddle turns dirty or the tungsten touches the work, stop and correct the cause instead of burying the defect under more filler.

A TIG argon regulator with a flowmeter makes gas setup easier to repeat. Also budget for a pedal, a suitable TIG torch, tungsten electrodes, filler, and a dedicated stainless brush if they are not included. A bare-bones welder can look inexpensive until those essentials are added.

A practical buying decision

For a home fabricator building stainless headers and doing other steel TIG work, buy a 160–200 amp DC inverter with high-frequency start, a pedal, adjustable post-flow, and readily available torch consumables. Choose AC/DC only if aluminum is a real near-term need. A cheaper lift-start unit is reasonable for occasional work, but thin header tubing rewards reliable starts and fine current control. Spend the remaining budget on accurate fit-up, back-purge equipment, and practice coupons in the same material and thickness as the headers.