It's been a problem for quite some time: Mopar owners have been the last ones on the performance hard-parts list for too long. But the huge resurgence in interest has tweaked many in the aftermarket companies to step up their R&D and come up with well-thought-out products. Flowmaster Exhaust is one such company. Recently, it released its 3-inch exhaust system to fit B-Body Mopars and more is on the way. We heard from Flowmaster and saw the ad for its new system. It was time to put it to the test.
David Hoffman of Sebastopol, California, decided his performance-upgraded '70 Coronet R/T didn't have the sound he would have liked it to have. After some investigation, he discovered the exhaust system that came fitted to the car was not doing its job adequately. Sure, it sent the spent gasses out the back of the car, but he first noticed something wasn't quite right after a buddy pointed out the exhaust seemed to have a wheezing sound as though it were forcing the exhaust gasses out. Another indication was the performance didn't seem as crisp as other 440's he'd been in.
Upon closer inspection, he found that the system was a basic Chrysler dual-exhaust system using compression-bent tubing, factory Hemi mufflers, and 2 1/2-inch compression-bent tailpipes. It looked fine, but with the compressed pipe diameter constricted to 2 1/4 inches in the over-axle sections, the exhaust system was unnecessarily restricted. It was a typical, clean, musclecar muffler-shop installation. Compression-bent pipes are what most over-the-counter replacement pipes are, with the ridges formed on the inside of the bends, where the pipe is compressed. For stock and restoration purposes this may be fine, but for enthusiasts who are trying to squeeze every bit of performance from what they have, mandrel-bent pipes are a must. Mandrel-bent pipes are bent in a way that no wrinkling of the pipe occurs in the bends, and the exhaust flow is smooth for its entirety.
Before installing the exhaust...
Before installing the exhaust system you will need to fully read the instructional material from Flowmaster. They supply you the fasteners, hangers and hardware to do a first-class installation. Install Flowmaster's tailpipe hangers to the rear framerail.
By chance, Flowmaster was looking for a B-Body Mopar to test fit a production version of their new Delta Force 3-inch exhaust system. So, David and Flowmaster got together and the test began. During the time of the exhaust install, David also installed tti headers.
The idea was to baseline test the stoutly built 440 on their new chassis dyno and then fit David's R/T with Flowmaster's new 3-inch B-Body performance exhaust and then dyno it again. This would quantify and evaluate any performance gains. To kick off the process, the dyno team strapped the R/T onto their new SuperFlo SF-840 chassis dyno. This rolling road is an inertia-weight dyno that is used in conjunction with eddy-current brakes. It offers accurate testing of acceleration, step testing, steady state full-throttle testing, and coast-down. It efficiently calculates rear-wheel horsepower right on the screen, and can calculate flywheel horsepower, as well. With an array of sensors, the dyno also allows for the precise measurement of backpressure, air/fuel ratio, and all engine temperatures, pressures and speeds through its 50 channels of data input. The baseline testing with its "as fitted" system tallied results of 288.9 hp and 365.5 lb-ft of torque. With that done, the R/T was put on the hoist for the installation of the new 3-inch Delta Force B-Body exhaust system.
Next, with a 3/8-inch bolt,...
Next, with a 3/8-inch bolt, install the supplied muffler hangers to the factory location, just ahead of the rear axle. Now, slide the rubber hanger onto the hanger mount. Then slip the clamp/hanger into the bottom hole of the rubber mount. These ring-type clamps offer superior sealing and clamp load over any other type of clamps.
With the muffler hangers in...
With the muffler hangers in place you can slip the mufflers up into their home. Snug the clamps around the mufflers to hold them in place. We were fortunate enough to have a lift, but if you're flat-backing it, jack stands can support the mufflers.
Now, you can move to the rear...
Now, you can move to the rear of the car and install the tailpipes. Slip the tailpipe up over the axle and into the muffler. If you're doing this without a lift, it may take some finesse to get the tailpipe up and over the axle housing.
Next, slip the muffler clamps...
Next, slip the muffler clamps over the muffler inlets, and then install the fixture-welded H-pipe assembly into the mufflers. Again, only snug the clamps.
Insert the tailpipe into the...
Insert the tailpipe into the muffler and then the tailpipe hanger rod goes into the rubber isolator at the rear of the frame.
Now, move to the front of...
Now, move to the front of the vehicle and install the intermediate-to-header connector pipes. With the mufflers, H-pipe assembly, and tailpipes centered with adequate clearance, mock up the connector pipes from the H-pipe-to-header collectors and cut them to length.