Tom Wilson
April 1, 2009
This is the engine configuration that launched an entire aftermarket industry-the mass air-equipped 5.0 H.O. Even if you've been around 5.0 Foxes for a while, it's unlikely you've seen too many that are stock. That's a tribute to how adding a tunable fuel-injection to the familiar small-block Ford eased the hot rodder's journey from carburetors to fuel injection. Today it seems simple, but when the original speed-density system debuted in '86, the knee-jerk reaction was to rip off the EFI and add a carburetor. Mass air changed all that and allowed the 5.0 to supplant the small-block Chevy as the mainstream engine for bolt-on speed.

Like it or not, 1985 saw the final carbureted Mustang. As was then normal, the front grille was restyled, 10-hole; 15-inch wheels introduced with the fast-wearing Goodyear Gatorbacks; and the swaybars enlarged and kicker shocks added to the rear suspension to combat wheel hop. All good changes, but the gear heads were mainly under the hood. There the roller cam made its debut, and this was heady stuff. Until then roller cams were race-car-exotic, but as the world was on the cusp of computer-driven leaps in precision and knowledge, the production roller cam marked the beginning of a real change in hardware and electronics.

That wasn't all, though. The once ubiquitous, heavy-as-sin cast iron exhaust manifolds were replaced by flyweight stainless steel short-tube headers-another amazement, headers on a production car-plus dual mufflers (although a central catalytic converter remained). Power jumped to 210 hp at 4,400 rpm, with torque moving from 245 lb ft in 1984 to 270 lb ft at 3,200 rpm in 1985.

Now here was a Mustang to be proud of. While still eclipsed by the big-block gods of the past in acceleration and panache, the 1985 Mustang GT with five-speed manual ran hard enough to demand respect, and was unquestionably better in the corners and at the gas pump. By comparision the CFI automatic 5.0s were still wheezing along with 165 hp in 1985. At a 45 hp deficit, EFI wasn't making any friends.

Having finally assembled a good-looking, hard-running V-8 Mustang with a five-speed and easy-to-work on carbureted induction Ford ticked everyone off by throwing it all away just a year later. For 1986 the Holley was gone forever, replaced by yet another EFI system. This one was even more complex with injectors at every port and sequential electronic activation. Furthermore, the ignition and fuel systems were co-mingled by a central engine management computer. Called EEC-IV, the new system was inscrutable, and punished anything past the most minor changes with hideous, stuttering driveability, flat spots and a lack of power. It was as if everything the hot rodder had learned was now useless, along with his tach/dwell meter.

Dig those 15-inch pony wheels; they were the nuts in 1991 and foreshadowed the iconic Cobra R rim. They were also the final cosmetic Fox Mustang change, save the Cobra-and along with the smooth nosed, body-clad GT trim seen here set the "modern" 5.0 look that took us to the SN95.

Also unfortunate was Ford's one-year switch to a dumb cylinder head. Similar to previous castings, the '86 head featured a fence around the intake valve in the combustion chamber. This masked-valve design promoted a high-swirl combustion chamber that was good for emissions but choked power, which backed up to 200 hp. Enthusiasts groaned; would old cars always be the fast way?

And these weren't just car enthusiasts; they were Ford enthusiasts. Ever since the '55 Chevy the domestic performance world was Chevy's oyster. Fords and Dodges were "other" cars. Chevy's were notable cheaper to buy and hot rod, ran as fast as anything and were the undisputed dominators in the performance marketplace. Ford fans typically came from Ford families, or had long ties to the marque at the least. To have a Mustang that made sense in '85 was a big boost to the faithful; to have it back-track in '86 was an insult.

The one bright spot in '86 was torque. The port injection system allowed the use of a long-runner intake manifold because it ran dry (no fuel mixture), so long, turning runner shapes could be run with impunity. The long runners promoted torque (and suppressed top-end power). Also, Ford had been creeping up the 5.0 HO's compression ratio, with '86 seeing a move to 9.2:1 from forged, flat-top pistons. Combined with the long runners, the '86 HO moved up to 285 lb-ft of torque; that helped cover up the power loss, felt good around town, and delivered a hair more fuel economy. Of course, by then fuel prices were falling in real terms as the economy started to recover, so that gain wasn't well celebrated.