At Burns Stainless, a merge collector is not just two tubes welded together. It is a precision exhaust component built to improve flow, fit, and performance. In this article of Vince in Shorts, Vince Roman walks through the process of building a 2-into-1 merge collector from raw merge bends to a finished, polished part.
It Starts With Layout
The process begins by applying blue Dykem to the merge bends. This makes the scored cut lines easy to see and helps keep the layout accurate.
Burns merge bends use a four-inch leg and a five-inch leg. The four-inch leg is the clamp end and should be used as the inlet side of the collector. That detail matters. Using the wrong end can distort the slip fit, especially when the collector is later expanded to fit over the primary tubes.
The longer five-inch leg is used where more material is needed, especially when reducing down to a smaller collector outlet.
Cutting and Fitting the Collector
The cut line depends on the gap between the two inlets. In this example, the collector is set up with a 1/8-inch gap between the tubes. Once the inlets are expanded for .065-inch wall material, the tubes will sit very close to each other.
Burns uses this spacing to account for weld shrinkage. Stainless steel moves during welding, and ignoring that movement can lead to poor fitment.
After scoring the cut line, the tubes are taken to the vertical band saw for the initial cut. The cut is made close to the line, but not directly on it. Final shaping is done on the grinding wheel, where each tube is carefully brought up to the scored line.
Once both bends are cut and shaped, the pieces are fit together so the seams are tight and clean.
Deburring, Tacking, and TIG Welding
Before welding, the cut edges are deburred and cleaned. A clean joint is essential for a clean weld.
The two tubes are then fit together with a shim used to hold the bottom of the collector open. A piece of tubing or a flange helps close the top gap while the collector is tacked. The top is usually tacked first, followed by additional tacks down each side.
Once the collector is secure, it is TIG welded.
One of the most important steps is back purging. This is critical when welding stainless steel. Burns blocks the outlet end and uses silicone plugs with purge gas flowing through the collector. This protects the inside of the weld and helps maintain the integrity of the stainless steel.
Cutting the Inlet and Outlet
After welding, the collector is cut to final length.
For the outlet, a piece of tubing matching the outlet size is used to find the correct location. Burns adds a quarter inch to that mark before scoring and cutting.
On the inlet side, Burns typically builds collectors with two-inch slips and a quarter-inch lead-in. That means the inlet legs are cut to 2.25 inches. A height gauge is used to score the cut line before the final cuts are made.
Rounding, Expanding, and Finishing
After welding and cutting, the outlet is usually oval rather than perfectly round. Burns uses a hydraulic press with dedicated tooling to form the outlet back into a round shape.
Next, the inlets are expanded so they slip properly over the primary tubes. Burns uses a finger expander for this step, carefully working the collector so both inlets come out parallel despite the natural distortion caused by welding.
A sample tube is used to confirm proper slip fit.
Then comes one of the hallmarks of a Burns Stainless merge collector: the polished interior. The inside is hand-finished in multiple steps, beginning with a sanding drum and followed by a flap wheel. The goal is a clean, smooth transition through the collector with crisp seams and no rough edges.
The outlet is checked again with tubing and fine-tuned by hand until the shape and size are right.
The Burns Stainless Difference
A finished Burns Stainless 2-into-1 merge collector is the result of careful layout, precise cutting, TIG welding, proper back purging, controlled expansion, and hand finishing. Every detail matters because every detail affects fit, flow, and durability.
That is what separates a true merge collector from a simple welded junction. At Burns Stainless, the difference is in the process.
