Take any 14-year-old truck and chances are the exhaust has seen better days. Such was the case for this '90 Bronco 4x4, but we didn't just want to replace the stock system, so we opted to improve it with a more efficient and powerful system. That's where Flowmaster comes in. Combining some online research with the experience of listening to Flowmaster-equipped vehicles in person, we decided that an after-cat system would be the perfect addition for this Bronco.
Flowmaster, founded in 1983, has just about dominated the racing market and, with its distinctive sound and proven reliability, seems to be the muffler of choice for hot-rodded street cars. After studying the Flowmaster website (www.flowmastermufflers.com), the decision to select the Force II system, which is designed for '87-'96 Ford Broncos with 5.0L and 5.8L engines, was pretty easy. This kit included heavy-duty 0.075-inch-thick walls, aluminized pipes, and a Flowmaster muffler. It also includes all of the clamps, hangers, and brackets needed for the job. The aluminized pipes will add durability to the system, and since we didn't plan on babying this rig, that's a good thing.
One benefit of ordering a complete system from Flowmaster is that everything is included and the pipes are mandrel-bent for a perfect fit and the best performance possible. Flowmaster says its system outperforms most OE and competitive aftermarket systems because every Flowmaster system is designed and tested for each specific application. Even the length of the tailpipe is considered because this can be an aid in keeping atmospheric pressure from rushing back into the muffler. Tailpipes can improve performance and control sound when they are designed correctly. As a rule, Flowmaster says tailpipes should be a minimum of 10 inches and no longer than 6 feet. If your tailpipe length has to be more than 6 feet, you may need to add a resonator. Thankfully, when you order a kit, it's all figured out for you.
The size of pipe used in an exhaust system is another critical item to consider. When you see import fans with their trash-can-sized exhaust systems, it seems like a somewhat logical conclusion that bigger is better. But, while pipe diameter will affect the sound level and performance characteristics of the muffler, it is important to understand that bigger is not always better. A pipe too large can actually hinder exhaust scavenging by allowing atmospheric pressure up the pipe. As a rule, most general street applications use 2- through 2.5-inch pipe, while modified street applications will generally use 2.5- or 3-inch-wide pipe.
The muffler, the heart of the system, may look simple when you see a drawing of the internals, but it has taken many years of intense research at Flowmaster to develop the patented technology that uses the pressure and sound energy released from an engine's combustion chamber into the exhaust system to create a low-pressure area between exhaust pulses. Flowmaster's designs use this energy to scavenge, or pull spent gases out of the cylinder. Flowmaster says it's even more efficient than an open-pipe system. And Flowmaster would know, as it has used track, highway, and dyno testing to prove its designs.
The bottom line is that the Flowmaster kit bolts right on with no fabrication required, it will last a long time, and the sound has just enough of an edge on it to make this Bronco sound more impressive than it is. Follow along as we install the Flowmaster kit on this '90 Bronco.
 Flowmaster's Force II kit...  Flowmaster's Force II kit for the '87-'96 Ford Bronco includes everything needed to install the after-cat system yourself. |
 After searchin the internet...  After searchin the internet to make a decision on which parts to use on this '90 Bronco, we eagerly awaited the UPS driver. |
 Here are the tools that might...  Here are the tools that might be needed if installing at home: jack, jackstands, wrench, air wrench, Sawzall, WD-40, prybar, and flashlight. |
 The original exhaust was simply...  The original exhaust was simply worn out. The truck owner went to AE Automotive in Huntington Beach, California, to have the kit installed. |
 The 14-year-old brackets were...  The 14-year-old brackets were in no mood to allow us to unbolt them. We used the hot wrench to blow the heads off the bolts. |
 A Sawzall had to be brought...  A Sawzall had to be brought into service to get the original system off of the truck |
 WD-40 was sprayed on the rubber...  WD-40 was sprayed on the rubber hanger to try and free it up. |
 A long prybar was used to...  A long prybar was used to loosen the exhaust. |
 The original muffler had more...  The original muffler had more than a few holes blown through it. |
 We were more than happy to...  We were more than happy to hand the old muffler over to the trash guys. Some cities consider a muffler hazardous waste, so make sure you know the law before you throw it in the trash and find yourself with an expensive ticket. |
 The kit comes with a Super...  The kit comes with a Super 50 series muffler, but the owner of this truck wanted a smaller muffler with a more authoritative sound, so he swapped the kit muffler for a black Super 40 muffler at AE Automotive, where the install was performed. |
 The Super 40 muffler was slid...  The Super 40 muffler was slid into position while all other connections were checked. |
 The frame created a bit of...  The frame created a bit of interference and we had to be careful to angle the muffler correctly so it wouldn't rub the frame. |
 A couple of tack welds were...  A couple of tack welds were used to position the Super 40 muffler. After everything was hooked up and the fitment was determined to be correct, it was fully welded. |
 The exhaust pipe was attached...  The exhaust pipe was attached to the muffler. It was a single pipe out of the muffler. |
 The clamps were tightened...  The clamps were tightened with an air wrench, while the exhaust pipe was held in proper alignment. |
 The finished system was a...  The finished system was a perfect fit and helped make this truck sound pretty tough. The results were exactly as anticipated. |