What is it about classic Fox-body Mustangs that makes us want to buy, build, and drive one? For one thing, these good-looking late-model rides are plentiful and cheap because Ford built so many of them from 1979-'93. Unless you have something more specific in mind, such as an '82-'85 GT, '84 20th Anniversary Edition, or the collectible '84-'86 SVO, the most popular Fox-bodies are the '86-'93 fuel-injected GTs and LX 5.0s.
The 5.0 Fox-bodies came with a true catalytic dual exhaust system that, aside from hanger configuration, didn't change much from '86 to '93. In the factory four-cat system, you have two "light-off" three-way cats at the headers. Further back at the crossover, they have more conventional cats on each side that connect to low-restriction mufflers.
If you live in 49 states, your options from Summit Racing Equipment are plenty. However, if you live in California, you are limited by law to the stock four-cat system, which will have to be fabricated by an exhaust shop using California smog legal catalytic converters unless you can find a new-old-stock cat package.
What makes these late-model ponies challenging to build and restore is the availability of parts, which is getting better with time as the demand for parts rises and the system endeavors to catch up. Gil Roiz found his '89 Mustang GT convertible for $500 in a "get it out of my driveway" deal. Although the car needed work, Gil was able to put it on the road for under $1,000. There are a lot of deals like this out there for Fox classics thanks to rough times and a large inventory of good buys looking for new homes.
In the July issue, we installed a Centerforce Dual-Friction clutch in Gil's 5.0L GT convertible. This month, we're going to get Gil into a new dual exhaust system from Summit Racing Equipment, which consists of a 49-state legal BBK catalytic converter package and the Flowmaster Force II cat-back system with Series 50 Delta Flow mufflers. At the engine, we're adding JBA shorty headers that are ceramic-coated for good looks and durability. This is a project you can undertake in your home garage in a matter of hours.
1 JBA Performance’s 50-state...
1 JBA Performance’s 50-state legal Cat-4ward stainless steel shorty headers, shown here in Titanium ceramic, deliver more horsepower and torque thanks to 1-5⁄8-inch primary tubes into collectors designed to fit stock and aftermarket exhaust systems. JBA has set the standard for header quality with fully welded 3⁄8-inch thick flanges, ceramic coating, Firecone design, and stainless steel construction. Priced at $748, they will last the life of your Mustang.
2 Here’s the 49-state legal...
2 Here’s the 49-state legal BBK Performance #1509 CNC Series Short High-Flow catalytic converter package with 2-1/2-inch plumbing for Fox-body Mustangs. The BBK cat package is not smog legal in California, where the stock four-cat package is mandatory. We’re not sure when the exhaust hangers changed from parallel hangers (#1509) to perpendicular hangers. However, if you have perpendicular hangers, you will want the BBK Performance #1563 cat package. California enthusiasts will have to have an exhaust shop fabricate a four-cat package from scratch using smog-legal cats because we haven’t been able to local a complete four-cat H-pipe package from the aftermarket. If you can find a new-old-stock four-cat H-pipe package for your Fox-body Mustang, buy it. You can get into the BBK cat system for under $400.
3 We’re fitting Gil’s GT...
3 We’re fitting Gil’s GT with the 2-1/2-inch Flowmaster Force II system (#FLO-17106) from Summit Racing Equipment. This system practically hangs itself using your Mustang’s stock rubber hangers. Because it is a 2-1/2-inch system, clearances are tight, which means you must pay close attention to distances between pipes, mufflers, and floorpan. This is the Flowmaster Series 50 Delta Flow muffler, which reduces noise and resonance while improving the Flowmaster’s legendary throaty sound. You can get into this cat-back package for $399.95.
4 Gil removes the old tailpipes...
4 Gil removes the old tailpipes using a fine-tooth saber saw just aft of the mufflers. WD-40 is used to soften the hangers.
5 This old replacement cat...
5 This old replacement cat package was crumbling right before our eyes so it needed to be replaced. The BBK Performance #1509 or #1536 cat package will help Gil’s ’89 GT get back to quiet operation along with cleaner emissions.
6 Collectors are disconnected...
6 Collectors are disconnected just ahead of the mufflers with a 9⁄16-inch box-end wrench and deep-well socket.
7 The old mufflers are unhinged...
7 The old mufflers are unhinged off stock rubber hangers. The nice thing about late-model exhaust systems is ease of replacement. You can do this yourself.
8 Oxygen sensors are disconnected...
8 Oxygen sensors are disconnected and removed on both sides. There are two. A 13⁄16-inch open-end wrench gets each sensor. This is a good time to replace your O2 sensors.
9 The air pump injection...
9 The air pump injection tube is disconnected next. The Thermactor air injection system feeds air into the exhaust system between the catalytic converters to further complete combustion of hot gasses and reducing emissions.
10 The H-pipe is disconnected...
10 The H-pipe is disconnected at the factory shorty headers. Gil used plenty of WD-40 on his factory header collector bolts before loosening.
11 The cat package is removed...
11 The cat package is removed and tossed. Note this is a replacement system with only two catalysts.
12 We’re going to replace...
12 We’re going to replace Gil’s stock shorty exhaust headers with JBA Titanium shorties, which will improve exhaust scavenging and improve both torque and horsepower. Gil goes for the factory header bolts using a deep-well 9⁄16-inch socket.
13 Check out the difference...
13 Check out the difference between JBA stainless shorties (below) and the stock headers. The small primary tubes from the factory greatly limited flow. JBA shorties will relieve flow restrictions and give Gil more horsepower and torque.
14 Installation is easy thanks...
14 Installation is easy thanks to JBA’s thoughtful engineering and years of testing. New gaskets are included in the kit. JBA has always been an enthusiast-owned and operated company, hence close attention to design and manufacturing. Gil suggests anti-cease compound on header bolt threads, especially if you’re running aluminum heads.
15 The dipstick tube must...
15 The dipstick tube must be modified to clear the JBA shorty flanges. Header bolts are tightened using a 3⁄8-inch open-end wrench. A 3⁄8-inch socket or box-end wrench will not fit.
16 To access the right-hand...
16 To access the right-hand header, induction and air pump plumbing must be removed.
17 The right-side factory...
17 The right-side factory header is removed using a 9⁄16-inch deep-well socket.
18 The JBA shorty header...
18 The JBA shorty header is a perfect fit, dropping right in before tightening the bolts with a 3⁄8-inch open-end wrench.
19 This early-style H-pipe...
19 This early-style H-pipe hanger had us baffled for a moment. As you can see, the rubber-lined exhaust hanger bracket is turned downward, which is incorrect. This bracket is marked “LEFT,” which indicates which side “LEFT” should be on as the driver faces the steering wheel. These bracket loops should be turned up, with “LEFT” on the left-hand side.
20 Exhaust header extensions...
20 Exhaust header extensions are loosely installed for ease of positioning. Because headers and tubes are beveled, no donuts are required.
21 Gil installs the cat H-pipe...
21 Gil installs the cat H-pipe hanger bracket. At press time, reproduction insulators are not available for this application so Gil used air-conditioning hose for insulation. You can also use fuel or cooling system hose. Gil tells us A/C hose works quite well and he’s enjoying a quiet ride.
22 The BBK Performance cat...
22 The BBK Performance cat package is carefully fitted to clear the floorpan and framerails.
23 Here’s a slick BBK slip-coupling...
23 Here’s a slick BBK slip-coupling borrowed from the aviation parts bin and the ’05-’11 Mustang. A slip-coupling makes exhaust system removal and installation easier than ever. Keep these couplings loose until it’s time to adjust the entire system.
24 Air pump plumbing is connected...
24 Air pump plumbing is connected using hose and clamps provided.
25 Fox-body Mustangs call...
25 Fox-body Mustangs call for the black rubber hanger for mufflers and tailpipes—E6ZC-5F262-AA, which may not be available any longer from Ford. However, if you go to the late-model F-Series truck parts bin and locate this brown steel reinforced hanger (#F81A-5A262-EV), it fits well and will outlast the original rubber versions. Another option is the Flowmaster HA-168 hanger, which replaces the E6ZC-5F262-AA.
26 Flowmaster Series 50 Delta...
26 Flowmaster Series 50 Delta Flow mufflers and pipes fit nicely with very few interference issues. Because they feature 2-1/2-inch pipes, expect them to be tight in places. You want a minimum of 1/4 inch between mufflers and floorpan.
27 Stock hangers and brackets...
27 Stock hangers and brackets bolt to the Flowmaster system.
28 Tailpipes slip right into...
28 Tailpipes slip right into the Series 50 Delta Flow mufflers. Don’t tighten clamps until clearances and fit are established.