Hooker Maximum Flow Straight-Through Mufflers - Pipe It Up

Any time you hang a fresh set of pipes beneath your floorboards, it's a very good day. Foreshadowing the burbly flow of cackling hydrocarbons that's about to ensue, it's a welcome sign that your project car is chugging down the home stretch toward completion. With the motor, trans, rearend, fuel system, suspension, rollcage, and cooling system already in place in our street/strip '93 Mustang project, we're itching to let it rip down the track. Since plans call for driving it 100 miles to the dragstrip and back, the auditory fury unleashed by its 532 ci and 273/280-at-.050 cam need to be tamed just enough to avoid unwanted attention. As with most engine swaps, however, routing fumes from the headers to the car's posterior isn't a mail-order affair. In the case of Project Fox, the situation is compounded by a rather large TH400 trans and beefy chromoly driveshaft that gobbles up lots of real estate in the trans tunnel, and a diminutive late-model chassis never intended to have massive dual 3.5-inch pipes crammed beneath it. Fortunately for us, the talented fabricators at Bill Buck Race Cars in Austin, Texas, were ready to take on the challenge.

The prevailing theme thus far with Project Fox has been keeping things simple and cheap, and designing a custom exhaust system was no exception. The setup we settled upon consists of 3 1/2-inch piping coming off of each header, and a pair of Hooker Maximum Flow straight-through mufflers dumping into turndowns positioned in front of the rearend. Much of the design was a product of necessity, as the space beneath the floorboards was further encroached by Project Fox's custom subframe connectors, heavy-duty drag sway bar, and the back bracing affixed to the rearend. Consequently, bends and kinks are virtually non-existent-which actually cut down on the installation time-and running the tailpipes over the rearend housing wasn't feasible. Compensating for the fact that a lack of over-axle pipes greatly increases the potential for annoying freeway resonance, we opted to run large oval mufflers instead of resonators. At the end of the day, the entire system was completed in about four hours, ringing up a tally of under $300.

Muffler Design Mufflers reduce exhaust noise through the use of absorptive materials, such as fiberglass, or with noise deflection chambers. Each technique has its advantages and disadvantages. Absorptive mufflers convert sound waves into heat energy, typically flow slightly better than chambered designs, and are less prone to resonance. The drawback is that their ability to reduce noise is compromised as the packing material begins to burn out. To combat this, Hooker uses high-temperature-resistant ceramic wool insulation, and some manufacturers rely on stainless steel insulation. Chambered muffler designs, on the other hand, won't burn out, but are more likely to resonate. For the best of both worlds, some designs use both chambers and sound-absorbing insulation. -Stephen Kim