2 3

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 straightforward.

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 are expensive.

Flowmaster's "U-Fit Dual Kit" Part No. 17588

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.

Flowmaster's "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.

Flowmaster 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.

2 3
In This Article:
Six months after retrieving Project MX, we reach our short-term goal of making this reckless acquistion more than another anchor in sideyard, driveway, or street.

Also see these articles for background on FM's Project MX.
Do You Need One More Project?
Project MX, Work Commences
An exhaust and valid registration were all that held us back from a maiden voyage. Mr. Z's muffler of Sparks, NV installed our Flowmaster exhaust system. Unfortunately, "contracting out" waiting in line for three hours at the Department of Motor Vehicles wasn't as easy.
A trip to the gas station can be a glorious experience if it's the first fill-up after reparing and registering a downbound project car.
Don't give us a hard time about the bad U-joints evident in this video, just focus on the exhaust.
In CHiP's-like fashion we made a few runs through some undeveloped Northern Reno suburban sprawl. Can't find open space like this in California anymore!












Tech Archives Project Cars Readers Cars Feature Cars