Model A & B

Ford Garage

Muffler Welds & Flanges

One of the topics often discussed is the construction of original and reproduction mufflers. The cheap $50 Model A mufflers have been shown to have excessive back pressure due to the design of the baffles inside. They are highly restrictive and nothing like the originals.

About 10 years ago Aries began reproducing Model A mufflers which are designed and produced according to the original Ford drawings, and many people have been choosing these mufflers in spite of their higher cost.

The Aries are the closest muffler available to match the original in construction, appearance, sound, and performance. There have been several dynamometer tests done demonstrating the improved performance of the Aries muffler compared to the cheap reproduction.

The main aspects of reproduction mufflers which are not quite like the originals are the tube welds and the inlet flange shape.

Pictured above is a view of the original muffler weld. This process is an electric arc resistance weld similar to what Ford did on many parts, both chassis and sheetmetal like wheel spokes and body side outer upper and lower panels.

The parts are clamped in a fixture and brought together while passing a large current through the interface. The resistance heat and contact force welds the two parts together.

There is no rod or filler metal involved in the resistance weld. The two parts provide all the metal used in the weld.

In the pic above the deformation of the tube outward at the weld is also seen on each side of the weld flash.

Pictured above are the welds on an Aries reproduction muffler I bought.

These welds are not resistance welded, but instead are MIG welded it appears. They also could be TIG welded, but in either case they use an added filler process and have a different appearance to the original.

Pictured above is the detail of an original Model B muffler inlet flange. This shows clearly the large size and shape of the flange.

Virtually all reproductions I have seen have a much smaller and poorly formed flange, frequently with the wrong angle.

The size and shape of the flange is critical for robust sealing of the muffler to the exhaust manifold, and is the source of a lot of muffler fit issues.

The pic above shows some simple tools I made to resize the shape of the muffler flange.

I found a large 3/4 drive socket at the used tool store which had a shoulder and taper near the same size as the tube.

I had a friend cut the socket to match the correct flange angle. This could then be used as a die for reforming the angle on an existing tube.

I then took a pair of two-piece shaft collars the same as the OD of the tube and clamped them below the flange to support the tube in a press.

By supporting the tube at the shaft collars and applying a force to the socket in the tube, the flange size and shape can be slightly reformed and improved.

Other restorers have also had good luck finding local muffler shops which could reform the flanges using their professional equipment.


January 2002