by Jon Mikelonis
When FordMuscle left off with Project MX we had fired up our
reconditioned 351 Cleveland and only needed an exhaust and
current tags to make the lucky rig roadworthy. Long-term intentions
of building a robust mill for the Montego meant that all significant
short-term upgrades were to be made assuming we'd eventually
have to accomodate more power. In some cases, like the exhaust
for instance, it made no sense to spend money twice. For this
reason, we chose a quality system, all the while knowing the
potential benefits might not influence our Cleveland in its'
almost stock form. Exhaust was one area we did not want to
waste time installing a temporary solution. FM teamed up with
Flowmaster to try out their new "U-Fit Dual Kit",
a universal mandrel bent dual exhaust kit specifically designed
for obscure american musclecars and trucks. Project MX was
an ideal candidate.
About Mandrel Bending
Talk exhaust with enthusiasts and you'll probably hear the
term, "mandrel bent". This is true across both the
hot rod and import scenes and is quite often a bullet point
listed in many a hobbyist's "For Sale" ads. As opposed
to the very common "empty" or "crush"
bending technique, a mandrel bent exhaust retains a common
inside diameter throughout the bends. Mandrel bent systems
do increase performance since a constant pipe diameter reduces
restrictions. Consider this, if you've determined a 3"
exhaust is what your motor needs, then why cheat yourself
with a piece of tubing that will be crushed down to 2.25"
in a number of locations along the system?
"An exhaust that maintains a common inside diameter
throughout the bends, serves to maintain the velocity of the
exhaust gasses travelling through them."
Mandrel bending can create a bend much tighter than empty
bending and also improves the appearance of the finished exhaust.
Radii as tight as one times the diameter of the tube are possible,
whereas with empty bending, acceptable radii are usually two
to three times the diameter. Mandrel bending is especially
suited for automotive exhaust applications where a complete
over-the-axle system can make for some sharp turns. As the
figure below shows, the concept of mandrel bending is fairly
Many people confuse mandrels with bending dies or shoes. Technically,
the mandrel is a part of the tooling set but does not exist
in most bending applications. The mandrel actually goes inside
the tube and is held by a mandrel rod to support the tube
at the tangent point of the bend. The mandrel is then extracted
after the bend is complete or within the last few degrees
of bending. This requires a machine with a bed longer than
the tube being bent and strong enough to support the forces
against the mandrel. Therefore, even the most humble models
Due to the high price, you'll find that almost all local
exhaust shops do not have a mandrel bender as a part of their
standard equipment. So, if you're determined to have a mandrel
bent exhaust, you'll need to seek out a specialized shop to
do the work. Another option is to acquire a mandrel bent kit,
like the one shown here, and install it yourself or find a
performance-oriented local shop to do the work for you. This
is the route we went down for Project MX. The universal nature
of this Flowmaster kit is simply perfect for oddball musclecars
like FM's 72 Montego.
Assume that even if you work with a performance shop, building
a dual exhaust with a kit is not going to be the way they
are accustomed to doing things. A universal kit will involve
some initial contemplation and study on the tech's part and
perhaps you'll be asked that question you've probably heard
all too often from service shops... "Now, are you sure
you want us to do it this way?" Say yes if you want performance
or the satisfaction that you'll have an efficient system to
accomodate a future build-up.
"Header Collector Ball Flange Kit"
Part No. 15925
Header Collector Ball Flange Kit
Another clever piece from Flowmaster that we incorporated
for Project MX was their Header Collector Ball Flange Kit
for 3" collector and 2.5" System. If you have problems
with leaking collector gaskets or if you are trashing your
collector flanges from bottoming out, then the kit shown here
will save you some headaches. The kit creates a worry-free
seal between your headers and pipes by incorporating a pair
of gasketless adpaters. You'll need to cut the collector flange
off your headers to make it work. We've included the ball
flange kit in the install on the following pages but check
out the drawing below for a quick understanding. Please note
that for informational purposes the adapters are shown rotated
90 degrees. For added ground clearance the flanges are installed
parallel to the street.
Part No. 942551
Choosing the right muffler to suit your personal taste and
application can be a paralyzing proposition considering the
market's offerings. For our Mercury, we wanted a traditional
musclecar sound and feel without interior resonance. In our
opinion, there is really no challenging the fact that Flowmaster
offers some of the best sounding mufflers. For a moment, we
were torn between Flowmaster's more aggressive sounding 40-series
muffler and the milder 50-series muffler. It was probably
the "Brougham" badging on the once sedate Montego
that ultimately helped us choose the mellow but deep sounding
50-series mufflers. They just seemed more appropriate. Be
sure to view the sidebar video for sound samples. We're sure
you'll agree that FM made the right choice for Project MX.