1979 Ford Mustang GT Dyno Test Reveals Shockingly Low Horsepower

Fox body Ford Mustangs. Many people love them, some hate them, but wherever you stand, there’s no denying it became a definitive 1980s automotive icon. Forty years ago, if you drove a 5.0 Mustang you were a straight-up badass. That’s pretty bold, considering a 1985 Mustang GT had just 210 horsepower from the factory. Go back a few more years, though, and it gets worse. It gets so much worse.

The Earliest Days Of The Fox Body Mustang

A new video from Late Model Restoration (LMR) shows us just how bad it gets, courtesy of a dyno pull featuring the first year of the Fox body – 1979. Yes, for the casual gearheads out there, the car synonymous with the 1980s actually hit the road in 1979. In those earliest of days it had four square headlights, a chunky eggcrate grille, and on Cobra models, a big snake decal on the hood to mimic the big firebird design Pontiac used on the Trans Am. Such was life in the 1970s.

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It’s done just 12 miles in 32 years.

Back then, Cobra (not GT) was the flagship performance Mustang, but let’s not get too excited about that. Its 5.0-liter V8 engine was rated at just 140 horsepower from the factory. This was an era when automakers were struggling to meet expanding emissions regulations, and well, they hadn’t cracked the horsepower code just yet. The first Fox body basically had a carryover 5.0-liter V8 from the much-hated 1974-1978 Mustang II. But the story still gets worse from there.

Making horsepower is one thing, but getting it to the ground is another. The 1979 Mustang had manual or automatic transmissions available, and there were various options for the rear-end gearset. Depending on the selections, you could lose a fair chunk of power in the process. And since emission regulations were a thing, tall gears for low-rpm highway cruising were common. That’s great for fuel economy, but terrible for getting up to speed.

This 1979 Ford Mustang Is Nearly All Original.

That brings us to the crux of this post: the dyno pull. This particular Mustang Cobra actually looks really good; LMR did a minor cosmetic dress-up on the exterior but left the powertrain essentially stock. In the video, they mention a new water pump, new fuel pump, and a muffler being installed. As far as they know, the engine is completely stock right down to the original ignition timing. It has a C4 three-speed automatic transmission and a 7.5 rear end turning 2.47 gears. If you don’t know what that means, just know this – it’s pretty much the worst combination you can get for acceleration.

However, none of that stops this old 5.0 from singing on the dyno. Under full throttle it sounds like a proper muscle car, even squatting down as it runs through the gear. We’re even treated to some flames spitting from the new muffler. Maybe Ford underrated these cars from the factory?

In a word, nope.

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The results from the first pull show a maximum output of – wait for it – 123.4 hp at 3,600 rpm. Torque peaked at 210 pound-feet at 2,500 rpm. And a second dyno run was nearly identical with hp and torque up just a couple of digits. Keep in mind, that’s power at the rear wheels. If you factor in a 20% driveline loss, power at the crankshaft comes out to around 150 hp. Hey, maybe Ford did under-rate these cars!

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It was certainly a very uninspiring start to the Fox body era. But 14 years later, this same basic engine would make 235 hp in the 1993 Mustang SVT Cobra. And while Ford never confirmed anything regarding that car’s output, the SVT Cobra’s venerable 5.0-liter was thought to be underrated by about 50 hp. Two years after that, the old 5.0-liter pushrod V8 was retired from Mustang service, peaking at 240 horsepower for the 1995 SVT Cobra.

Source: Late Model Restoration / YouTube