How a Muffler is Manufactured
This article, by Joe Davis of Aries Limited, was originally
published in the Model A and Model T monthly.
Doug Clayton and I spent almost one year in 1983, researching every available source of information to be
able to re-manufacture a Model A muffler identical to the one made by Ford between 1927 and 1931.
Doug is and has been a judge for MAFCA for almost 20 years.
He had made many contacts and we were able to find two original mufflers, in addition to original blue prints.
The mufflers were, of course, rusty and not in the best of shape, but helped immensely in understanding the quality
of the metal work. Which was quite good for a muffler. Some of the features that are incorporated in both the
original muffler and our reproduction muffler include the following:
The mounting flange to the exhaust manifold requires
two operations, as the size of the flange is such that
the material must be annealed after the first pass to
avoid rupturing the metal. Other mufflers on the market
only make one pass and the resulting flange is not large
enough to form an effective seal. It also vibrates loose
and leaks profusely. There are many fixes to this problem,
but the real solution is to make the flange to specifications.
Our tubing is "mandrill bent." When tubing
is bent, it must be collapsed slightly on the inside
of the bend, in order to be forced around the bend.
This greatly reduces the cross-sectional area and restricts
the gas flow. Ford mandrill-bent all its muffler tail
and inlet pipes; we do the same. It requires taking
the conventionally bent tubing sections and placing
them into a die of the correct diameter and radius.
While restricted in the die on all sides, round steel
balls are forced through the inside of the tubing, bringing
it back to a full round shape by brute force. This is
a very slow process and greatly adds to the cost of
making these pipes. Today this process is only used
for precision tubing applications such as aircraft and
We assemble the components of the muffler in a master
fixture. The parts are guaranteed to be properly aligned
and thus fit correctly to the frame and manifold.
The tolerance called out on most of the drawings
are +/- 0.005 of an inch. This is about the diameter
of a human hair. We have quality systems in place to
meet military specifications to Mil 45208A. We make
the muffler in same environment as those parts
so the quality is built in.
The mufflers are made from A-36 cold rolled steel &
304 stainless steel. We now provide the steel muffler
painted with flat black, high temperature paint. This
is allowed by judging standards used by both MAFCA and
MARC. Our stainless muffler is lightly polished, but
can be painted if used on a car to be judged.
have complete blue prints on all components and the complete
assembly. We guarantee it to be exactly per the original