McLaren M81 Mustang

Imagine if Ford decided to not put a V8 in the 3rd Generation Mustang? 

In 1980 times were bleak for fans of American muscle. OPEC had given the Western hemisphere a considerable slap upside the head resulting in a change that would be felt for decades. Long gone were the big-block giants of the 60s and 70s. Engines and cars were getting smaller.

For the Mustang, this meant saying goodbye to the 5.0L V8. In 1980 the only V8 available for the Mustang was a destroked 4.2L wheezing out a miserable 118 hp. The only ‘performance’ engine available that year was the 2.3L four-cylinder turbo. Smaller displacing engines mated with forced induction were going to be the future of the pony car – at least that was the plan.

Ford wanted to bring more attention to the potential of the 2.3L Turbo. The realities of a recent energy crisis, and the emergence of more strict emission standards combined in a perfect storm against business-as-usual muscle cars. Gone were the days of ill-handling, tire-shredding sleds. The future was going to be smaller and nimble with an emphasis on handling. To generate excitement about the Mustang Ford green-lit a prototype to showcase this new direction.

The M81 is often cited as the first SVO vehicle. It’s understandable since the M81 was debuted in late 1980, and the announcement of the Special Vehicle Operations (SVO) division was announced in September 1980. However, the McLaren M81 was actually designed much earlier in the year. It’s somewhat of a “Chicken and the egg” scenario. Ford was pleased enough with the initial M81 to proceed with a competition effort, and the launch of the DSO (Dealer Special Order) program. SVO was involved with the competition variant (produced for IMSA GTO class) and many of the lessons learned there found a way into an SVO specific Mustang a couple of years later.

Todd Gerstenberger & Harry Wykes completed design of the M81 McLaren in the spring of 1980 and the prototype was featured in Ford’s traveling Motorsport cavalcade. The requirements from Ford—Emphasis on handling and using parts off the shelf of current inventory—were achieved, the prototype was very well received, and a limited edition of 249 vehicles was approved for production to begin in 1981. This car would be a joint venture between Ford’s newly revitalized Motorsports division (Ford had just ended a 10-year ban on factory-backed racing) and McLaren Engines of Livonia, Michigan.

McLaren Engines  blueprinted, polished, de-burred and reassembled an essentially stock variation of the 2.3L Turbo for the M81. At 5psi of boost, horsepower was comparable to a stock 2.3L turbo, but the extra attention from McLaren to the rolling assembly allowed the M81 to have a much higher and variable boost. The boost control was inside the car and adjustable from 5-11psi. Top output was estimated 175hp (Motor Trend magazine reported the adjustability of the boost up to 12psi and top horsepower at 190hp. 12/80)

From Wikipedia:
“Power was again provided by the turbo-four, but it was newly fortified with a variable boost control having a range of 5 psi (0.3 bar)-11 psi (0.8 bar) vs. the regular engine’s fixed 5 psi (0.3 bar). Rated output was 175 horsepower (130 kW) at 10 psi (0.7 bar), a big jump over the 132 horsepower (98 kW) stock mill.”

The T-3 Garret turbo head unit feeds the 9.0:1 C/R engine to create 145lbs of torque at just 3,000 rpm at the lowest boost setting. The 4-speed manual in the prototype will be replaced by a new 5-speed in the production models – all finding a final gear drive of 3.45:1. As tested by Motor Trend Magazine 12/80, the M81 Mustang went 0-60mph in 9.76 seconds, and completed the ¼ mile at 17.37 seconds and 79.20 mph – boost control was set at 7psi for this test.

Suspension: Fully adjustable Koni shocks and struts with unique (translation: this was the only part we couldn’t pull off the shelf) higher-rate springs. Sway bars borrowed from the police packaged Fairmont with tungsten bushings.

Wheels & Brakes: 3 piece BBK 15X8” wheels with 255/55/15 Firestone HPR tires. The production version of the M81 would use the same size single piece wheels, while the IMSA GTO entry would wear the same tires with 3 piece 15X9” wheels. Brakes for the production based M81 were 10.6” front rotors with semi-metallic brakepads, larger calipers borrowed from the V8 Mustang and 9” drums in the rear. For the IMSA GTO beefier Hurst/Airheart disc brakes front and rear.

Exterior: There is no mistaking an M81 from the outside (well, technically it could be mistaken for a DSO optioned mustang – see sidebar.) This Mustang received a lot of attention in the wind tunnel early during design. The fully functional extracting hood and chin spoiler plant the front of the Mustang with confidence at speed. Active front and rear brake ducts keep component temperatures down. And enormous steel fender flares stretch out to cover a wider than stock stance and 255/55 rubber.

Interior: The door panels, dash and center console are the same as a stock 2.3L turbo – but the interior feels noticeably different. To start, Recaro LS bucket seats are matched with the same cloth as the rear seat coverings. The steering wheel is smaller than stock – a 14” leather wheel from Racemark. The M81s offer an (at the time) SCCA approved bolt in roll bar. Instrumentation was changed to a unique Stewart-Warner panel specially made to integrate into the factory dash. A small brass plaque adorning the dash finishes the assortment of subtle interior enhancements.

You Can’t Believe Everything You Read: The M81 McLaren prototype Mustang had an ATL 18-gallon fuel cell with the filler neck passing through the center of the rear deck lid. According to the Motor Trend article from December 1980, this was going to be standard equipment for the M81. This feature did not reach production all models – the only white M81 McLaren ever produced wears a gas door held to the body with a piano hinge.

Production

Although 249 (plus one prototype) M81 Mustangs were scheduled for production, only 10 additional cars were produced. In total there were 7 created in Bittersweet Orange, 1- Black, 1-White, and 2- Enduros. Apparently the world wasn’t ready for a $25,000 hand-built Mustang. With so few vehicles ever made this is one of the most rare Mustangs ever built – so it should be a sure fire collectors item. Right? Well, not exactly. So few people have actually seen a McLaren M81 Mustang. There is not a lot of awareness of the car – and there is a relatively small (albeit devoted) following of early year Fox Mustangs. Even though this car would pave the way for a reentry into motor sports for Ford, and define much of what would become a future cult favorite – the Mustang SVO, the M81 never developed a Rock Star fan base – yet.

References

Wikipedia.com McLaren History
ASCMcLarenCoupe.com
FourEyedPride.com
Motor Trend Magazine – December, 1980
Tom S. Fotoki bucket – M81 Photos