NEW INSULATED MUFFLER SHIELD AND THE ARIES MUFFLER
A Combination That Beats the Heat (159 Degree Temperature
by LESLIE PAM
Shield-- click on an image to see an enlarged view.
cruising back from the National convention in Riverside,
with the temperature well over 100 degrees, I noticed that
my gas pedal foot was getting very hot, and I had to use
the hand throttle to go the rest of the way. It made me
wonder how many times we have heard that same complaint
about hot feet from our front seat passenger, while cruising
in the heat of a California summer. Like many others I have
considered a number of solutions-- ranging from muffler
shields and floorboard insulation to the firewall accessory
manufactured to fit the Model A. While I have tried all
or a combination of the above, in an attempt to make my
driver's compartment as free from heat and noise as possible,
I am going to restrict this article to our tests done on
different mufflers and shields.
Bob Travis and Bob Moore volunteered their sedans, as Travis
had the Aries muffler and Moore had a stock replacement
muffler. Most of the tests were going to be done on Travis
sedan, but I wanted a reading off of Moores stock
muffler for comparison.
Bob Travis and Bob Moore had the commercially-available
muffler shield already installed on their cars and I provided
an alternate choice with a prototype of my newly-designed
extreme-duty muffler shield. Having had a bracket failure
on the currently-available shield, I had decided to improve
on the design, and I conceived of creating the insulated
shield which I subsequently built and am currently running
on my own car. In the original shield, the sheet metal brackets
which are made of the same gauge as the shield itself are
spot welded and tend to crack, due to the flimsy nature
of the design. If you have one of those on your car I would
recommend checking for this problem, as Bob Travis
shield had a serious crack in the rear bracket which I pointed
out to him when we removed it for one of the tests. To eliminate
this problem on the new shield, I am fabricating 1/8 inch
steel brackets that are attached with 3/8 bolts. I also
wanted to create a more efficient insulated shield by sandwiching
a commercially-available heat-absorbing material between
two pieces of sheet metal.
get accurate readings on all the tests, I used a hand-held
infrared thermometer, with a laser to pinpoint the exact
spots we wanted to test. All measurements were made from
Traviss sedan has an Aries muffler and a 160 degree
thermostat, which kept the engine temperature at a constant
160 degrees. Bob Moores sedan has a stock muffler
and no thermostat, so we used a towel over the radiator
to keep his engine temp at 160 degrees. The temperatures
were checked periodically with the infrared thermometer
pointed to the center of the core.
when we started measuring the temperature off the muffler,
which was always done at the front and rear seams, we noticed
that when the engine was cold, the temperature was hotter
than when the engine warmed up. This is due to the effects
of scavenging. When the hot exhaust gases come into contact
with the cold manifold, exhaust pipe, and then muffler,
the gases condense, slowing down the flow, hence the higher
exhaust temperatures. After reaching operating temperatures,
the scavenging effect produces a faster flow and less heat
in your passenger compartment.
Bob Travis sedan measured 330 degrees at the front
seam of the muffler with the engine cold and 207 degrees
at the front seam when at 160 degrees operating temperature.
Bob Moores sedan went from 394 degrees at the front
seam with a cold engine to 289 degrees at the front seam
when at 160 degree operating temperature. It is interesting
to note the 82 degree differential between the Aries and
the more common replacement muffler after the cars reached
Traviss sedan with muffler temperature at front seam
read 207 degrees and as expected with no muffler shield,
207 degrees from the top side coming into contact with the
Traviss sedan with commercially available muffler
shield read 160 off shield coming off the front of the muffler,
which is a reduction of 47 degrees less heat than is coming
directly off the muffler.
Traviss sedan with my extreme duty muffler shield
read 130 off the shield coming off the front of the muffler,
which is a reduction of 77 degrees less heat than is directly
coming directly off the muffler.
Aries muffler runs 82 degrees cooler than the "other
muffler". The extreme duty shield gives you an additional
30 degrees of reduction over the "other shield".
reduction is 159 degrees with the extreme shield and Aries
muffler combination. That is 159 degrees of heat reduction
under the floorboards of your passengers feet.
Traviss sedan was also fitted with a special rubber
pad with 1/8 inch aluminized material bonded to the backside
that I designed to fit under the carpet and go up the entire
firewall from inside the car. He will test this combination
of extreme duty muffler shield and firewall kit throughout
the year as we need to put this combination to the summer
torture test. My own car has all of these modifications
and while coming back from last years Zaca Lake trip with
the temperature well over 105, my wife Ann never complained
about her hot feet. Either Bob Travis or I will be carrying
the infrared thermometer with us on club tours, so please
ask us to check the temperature of your floorboards in the
passenger area. Then decide if your passenger deserves the
time and effort to do this improvement. And please dont
take our word for it; ask Joyce or Ann, our better halves.
Moore is president and Bob Travis is technical advisor to
the Santa Anita A's Model A Ford Club, Arcadia, California.]
"KOOL FEET" Muffler shield is available from Leslie
Pam for $79.95.
Tel: 310-275-3836 Email: LAKoolp@pacbell.net