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Boss 6.0 – 1989 Ford Mustang LX 5.0

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Photography by Jeff Koch.

Looking back over the course of hot rodding’s history, it’s easy to spot the standout cars, the ones that fueled the movement, inspiring legions of young speed-seeking gearheads to spin wrenches and wield torches in the pursuit of ever improving performance. As grassroots-level auto racing evolved in this country, a mere handful of those cars emerged as icons of their respective eras, each serving as the “it” model to have if you were going to create a competition machine from a common passenger car. In the post-war era, it was the ’32 Ford; through the ’60s, it was the ’55 Chevy; for the ’70s, it was the ’69 Camaro.

But just as the practice of building hot rods out in the garage has continued forward, so too should entries to this exclusive club, and to that end, we’d nominate Ford’s Fox-era Mustang. While the significance of the 5.0 Mustang may not yet be as apparent as that of its forebears, there’s an argument to be made that its influence was as impactful during its day as any of the other touchstone machines had been during theirs. It’s the car most responsible for igniting the fire in a new generation of performance enthusiasts after the industry finally emerged from the muscle apocalypse of the mid-’70s and early ’80s. The five-liter Mustang was quick, it was durable, it responded to tinkering and tuning, and, perhaps best of all, it was cheap. By hitting those marks, the new-age Mustang was able to inspire renewed interest in drag racing, road racing, autocrossing, and whatever else you can do with a hot little car. This activity in turn motivated the performance aftermarket to create new lines of speed parts and equipment. By the early ’90s, the next mass movement in American muscle was hitting full stride.

Yet today, the Fox Mustang’s impact is often overlooked. It might be that, when viewed in retrospect from 2013, the ’79-’93 Mustangs can appear almost bland, with their conservative styling and modest 225hp engines. Factory performance cars certainly have evolved since the ’80s; to wit, today’s Mustang GT has double the horsepower of the 1985 model, while the current Shelby’s output more than triples that figure. In that light, even the pinnacle Fox, the ’93 Cobra with its 235hp, tends to look a bit meek.

But to anyone forced to suffer through the dark ages that followed the first muscle era, the Fox five-oh was a revelation, as Gary Tetu can attest. He’s witnessed just about the entire saga of factory performance, having reached driving age before the 1950s had drawn to a close. In proper form, one of his first cars was a ’55 Chevy purchased in 1961 and quickly fitted with a junkyard 327 to replace the Stovebolt Six. Clearly, the tendencies had been instilled in him early.

“The 327 bolted right up to the three-speed, and that made it a lot more fun car,” he recalled, reminiscing about the times he and a high school buddy had with it. But it was a relatively brief affair.

“My story is one you’ve heard over and over again,” offered Gary as he relayed the familiar phases his life transitioned through: school, military service, a wife and then kids. Practicality came to the forefront as it does for so many of us, and hot rods just didn’t fit into Gary’s maturing lifestyle.

1989 Ford Mustang LX 5.0 1989 Ford Mustang LX 5.0 1989 Ford Mustang LX 5.0 1989 Ford Mustang LX 5.0

But Gary’s story has other familiar turns, particularly the one where his kids get a little older, and life starts to smooth out a bit. “Once I felt like I didn’t have to drive station wagons all the time, I wanted to get something that resembled a hot car. Chevy had come out with the third-generation Camaro, so I bought a brand-new 1983 Z28 with a 305 and an automatic,” said Gary of his return to performance. Without prompting, he quickly pointed out that the automatic was a concession to his need to drive the new car daily in Phoenix commuter traffic, but that wasn’t the real issue with the Camaro.

“It looked cool, but it had terrible build quality. There were lots of issues, and I sorted through them, but that 305 didn’t have the performance I was looking for.” So, after getting his use from the Z28 for several years, it was time to shop for its replacement.

“When ’87 came along, the Camaro was still having issues, so I started looking away from General Motors for the first time in my life. I’d been reading great things about these Mustangs, and then they came out with fuel injection. So I thought, by ’87, they’d have the bugs worked out,” offered Gary of the reasoning that ultimately led him to purchase a new ’87 Mustang LX hatchback with the 5.0-liter engine.

“It was so much better built, and the performance was so much better,” he recalled of his first impressions. “I drove that car every day for four or five years and put 65,000 miles on it, and I don’t think I ever took it back to the dealer.”

But once those years and miles had passed, Gary was ready to move on. “It wasn’t a big thing; they were just cars then,” he said of his attitude at the time, though the LX never really faded from his memory. “A few years later, I thought back to how much I loved it,” he said, and here another familiar story began–the one where the guy realizes he wants a car just like the one he used to have. But once again, Gary would have to wait. “I had kids in college, so the timing wasn’t right.”

He flexed his patience by using the time to map out a plan. “When I finally got to a spot where I could buy one, I wanted a notchback, like I had wanted new,” he said, going on to explain that his ’87 hatchback had been selected for practical reasons since it offered plenty of room to carry stuff. Like the Camaro that had come before, that LX 5.0 was an automatic, but his next Mustang would be properly equipped with three pedals.

1989 Ford Mustang LX 5.0 1989 Ford Mustang LX 5.0 1989 Ford Mustang LX 5.0 1989 Ford Mustang LX 5.0

Before long, Gary had his ideal LX… or so he thought. “I bought a ’92 with 17,000 miles–gorgeous car. It turned out to be even better than the seller had related–just pristine condition,” he recounted, seeming to describe the perfect outcome…except for one thing. “I kept it for five years, but I couldn’t bring myself to hot rod it–I’d have felt like I was destroying a piece of hot rodding history, so I sold it.”

You see, Gary wasn’t looking for a straightforward nostalgia trip just to replay his experience with the ’87 LX–he wanted to build his version of the ultimate Fox Mustang. The recipe was quite simple: Add lots more power and leave everything else looking just as it had before. Even his strategy for obtaining that power was simple: no forced induction, no nitrous oxide, not even the classic 5.0 heads/cam/intake approach. Instead, Gary intended to swap the entire engine for one of Ford Racing’s current bullets: The Boss 363 crate engine.

“I knew Ford was going to replace its stroker 347 crate engine with the newly developed Boss 363,” Gary explained, “and I got to thinking how cool it would be to join a Fox-body Mustang like I loved back in ’87 with that 500 horsepower Boss crate engine to create the Boss Fox-body Mustang Ford never built.” Of course, he still needed a car.

This time he found a 16,000-mile ’89 LX notchback in nearly the same condition as the ’92 he let go. But there was just enough of a difference to make it right. “This one was almost as nice, but it had been messed with a little bit, so I didn’t have the same guilt.”

Shortly after getting the car home from Florida, Gary got in touch with local Ford expert, Rob Wetzel of Forced Induction Tuning. Once the project had been agreed to, Gary ordered the Boss crate engine while Rob started removing the original 5.0. The new engine arrived in only a week, allowing Rob to continue full steam ahead.

Ford Racing’s Boss 363, in spite of what its name might imply, is actually from the same engine family as the stock 302. The “Boss” part comes from the inclusion of Ford Racing’s relatively new Boss 302 engine block, which is not actually patterned after the legendary 1969-’70 version, a design that was somewhat unique in that it was configured to use Cleveland-style cylinder heads. Instead, the new Boss block is a fortified version of the standard Ford small-block, designed with more strength and durability and with improved oiling circuits, among other features. It was also designed to better accommodate stroker crankshafts and large over-bores, thus enabling it to reach 363 cubic inches, which answers another common question: No, this engine is not based on the 351 Windsor tall-deck small-block design.

1989 Ford Mustang LX 5.0 1989 Ford Mustang LX 5.0 1989 Ford Mustang LX 5.0 1989 Ford Mustang LX 5.0

All of that meant it was relatively simple to swap the crate engine in place of the stocker, and to disguise it as such. Of course, neither Gary nor Rob wanted to compromise the 363’s output by choking it with too-small factory intake and exhaust systems, and it would have to be properly fed, so Rob set out to equip the new engine appropriately, if subtly. To that end, an Edelbrock Victor EFI upper and lower intake manifold sits atop the engine, fitted with an Accufab 75mm throttle body. Ford Racing shorty headers look stock-ish, since Mustang 5.0 engines had tube headers from ’85 on, but these are larger and connect to an X-pipe, in turn feeding Flowmaster mufflers; stock tail pipes maintain the illusion out back.

There’s plenty more hardware supporting the 363, yet at the same time, this Mustang is devoid of so many items that seemed to have been deemed mandatory back during the height of the five-oh craze. You won’t find any trick suspension here–Gary even swapped the previous owner’s lowering springs to return the originals. No traction devices or steep gears either; Gary selected a set of 3.27s from the Ford Racing catalog to maintain all-around performance, leaving the rest of the stock rear axle alone. The original T-5 five-speed remains as well, though connected via a McLeod twin-disc clutch and shifted with a Hurst unit. Apart from the exhaust, only a set of Maximum Motorsports subframe connectors serves as an obvious deviation from stock underneath.

But that illusion is shattered when the key is turned, according to Gary. “Ford put quite a cam in that engine, and I wasn’t going to put stock mufflers on it, so when you start it the stock aura goes away,” he said, adding that, “There is some loss of drivability from the cam, but once you reach 2,000 RPM, it puts a smile on your face.”

Despite the upgrades and the significant increase in output, Gary has no current plans to go racing, though he estimates the re-powered Mustang should be good for low 12s as it sits (It has BFG Drag Radials on the rear at all times.), and “even faster with transmission, axle, traction and tire modifications.”

For now, Gary is content to enjoy his Fox on the street, experiencing the look and feel these cars offered back when they first instilled in their owners that time-honored urge to go ever faster. His Boss 6.0 creation clearly illustrates that the Fox Mustang remains a simple and effective weapon in the performance wars, one that has definitely left its mark on the history of hot rodding.


My concept for this car has largely been achieved. No huge hood scoops, large modern wheels, huge exhaust pipes, etc. The goal was never to build a race or track car of any kind; I wanted this car to remain factory-like and retain its original look, feel and character. This car still has all the charm of a 1989 Mustang 5.0 LX; however, when you start the engine, my Boss option becomes quite evident; even more so when you drive it. It’s a bit of a sleeper, and it sure is a lot of fun.–Gary Tetu

+ Sleeper vibe
+ Vast power on demand
+ Not too valuable to drive

– Easily overlooked
– Still waiting for Fox respect
– Not yet raced

1989 Ford Mustang LX 5.0 Specifications

Block type – Ford Racing “Boss 302” small-block, cast-iron
Cylinder heads – Ford Racing “Z” aluminum, 2.02/1.60-inch valves
Displacement – 363 cubic inches
Bore x stroke – 4.125 x 3.4 inches
Compression ratio – 10.0:1
Pistons – Mahle forged aluminum
Horsepower @ RPM – 500 @ 6,500
Torque @ RPM – 450 lbs.ft. @ 5,300
Camshaft type – Ford Racing hydraulic roller, .580/.602-inch lift, 232/240 degrees duration @ .050-inch lift
Valvetrain – Ford Racing 1.65:1 roller rocker arms
Fuel system – Walbro GSS 340 255-liter/hour electric fuel pump
Induction system – Edelbrock Victor EFI intake manifold, Accufab 75mm throttle body, injectors, C&L 85mm mass airflow meter
Ignition system – MSD Pro Billet distributor
Exhaust system – Ford Racing stainless-steel headers with 1-3/4-inch primaries, X-pipe, Flowmaster Super 40 mufflers, stock 2-1/4-inch tailpipes
Original engine – Ford 5.0-liter ( small-block V-8


Type – Ford/Borg-Warner T-5 World Class five-speed manual with McLeod twin-disc clutch
1st – 3.35:1
2nd – 1.99:1
3rd – 1.33:1
4th – 1.00:1
5th – 0.67:1
Reverse – 3.15:1

Type – Ford 8.8-inch differential with Traction-Lok limited-slip and 28-spline axles
Ratio – 3.27:1

Type – Ford rack-and-pinion with hydraulic power assist
Ratio – 15.0:1

Type – Power-assisted hydraulic disc/drum system
Front – Ford vented disc, 10.84-inch rotors with single-piston calipers
Rear – Ford drum, 9-inch

Front – Ford “Fox” platform modified McPherson strut with coil springs and 1.3-inch anti-roll bar
Rear – Ford four-link with coil springs, tubular shock absorbers
and .83-inch anti-roll bar

Wheels – Ford cast-aluminum “10-hole,” four-lug
Front – 15 x 7 inches
Rear – 15 x 7 inches
Tires – BFGoodrich radial
Front – 235/60-15 BFG Radial T/A
Rear – 235/60-15 BFG Drag Radial

– Not tested

This article originally appeared in the August, 2013 issue of Hemmings Muscle Machines.