Ford Authority

V10-Powered 1999 Ford Mustang Boss 351 Concept May Have Predicted The Future

A little over two decades ago, a group of engineers had the bright idea that a more serious Ford Mustang was needed to combat the Dodge Viper and Chevrolet Corvette. Something with a V10 engine, in fact, just like the Viper. Ford just so happened to have the 6.8L Triton V10 already in production, but that engine was far too tall to fit in the Mustang. So those engineers – in secret – began designing something that would.

To do that, the rogue group took the sand castings from Ford’s 4.6L V8 and simply added two more cylinders to produce a 351 cubic-inch, dual-overhead-cam, 5.8L V10 with modified Cobra R heads. The resulting powerplant was only slightly larger than the existing modular 4.6, and the team was able to stuff it under the hood of a 1999 Cobra R mule already in the shop.

The new V10 was backed up by a Tremec T56 six-speed manual transmission, which sent power back to a beefy Ford 9-inch rear end with 3.83 gears. The engineers even went so far as to upgrade the suspension and brakes on the Mustang, then gave it a set of Saleen wheels and a Cobra hood. The performance was impressive as well – 426 horsepower, 400 pound-feet of torque, and an 11-second quarter-mile.

Ford obviously never put the Mustang Boss 351 Concept into production, as it would’ve been prohibitively expensive to do so. But what makes it particularly interesting today is the fact that a V10-powered Ford Mustang might just be on the way. As we reported last week, Unifor president Jerry Dias stated that Ford is making a $148 million investment in the Ford Windsor Engine Plant which would be used to “source new 6.8L engines” to use in “derivatives for the Mustang and F-150.”

While the new 6.8 could be some sort of pushrod V8, as many are speculating, it just so happens to sport the same displacement as that old V10 engineers originally tried to shoehorn in the Mustang Boss 351 Concept over 20 years ago. So maybe, just maybe, those engineers were really building something that was far more ahead of its time than anyone realized back then.

We’ll have more cool concepts to share soon, so be sure to subscribe to Ford Authority for more Ford Mustang news and continuous Ford news coverage.

Brett's lost track of all the Fords he's owned over the years and how much he's spent modifying them, but his current money pits include an S550 Mustang and 13th gen F-150.

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  1. Roy Chile’s

    I remember the BOSS 351 concept the next BOSS should be a 351 or 429 model I wonder where the BOSS351 is today

  2. Mark L Bedel

    It’s always been about volumetric efficiency, and so it is today as well…

  3. Adam

    How do you relate a 6.8l OHC v10 to a 6.x liter OHV engine? Nothing else to write about I guess

    1. Brett Foote

      Well let’s see.

      1. Same displacement
      2. Ford has made a 6.8L V10 in the past.
      3. Ford tried to put that 6.8L V10 in a Mustang but it wouldn’t fit.
      4. Ford just signed a deal with Unifor that includes production of a new 6.8L engine that is slated to be used in an upcoming Mustang derivative.
      5. Nobody knows what kind of engine that new 6.8L will be, whether it be a V8, V10, OHC, DOHC, diesel, gas, etc.

      Good enough for you?

  4. Donald Hayes

    With the push of EV vehicles and States like california eliminating gasoline vehicle sales by 2035. I don’t see Ford adding larger gasoline engines to the Mustang unless it’s a limited production Mustang.

  5. Harold Stewart

    Hello….I remember that particular testing back then with the V10 powered Mustang running low 11s all day bringing it off the line at 4500 rpm until the clutch blew which was the weak part of the car….some smart fellow came up with the idea of replacing it with a twin disc unit afterwards bringing off the line at 5000 rpm going 10.80s …my hopes were up for this move by Ford that never happened and the motor was completely untouched….wow

  6. Steve Purcell

    I’m lucky enuf to own 3 very special Ford’s. I have RP1 Roush prototype 1 99 ford mustang that they used for development it’s like a stage 3 the bumper cover is fiberglass. I also have nightmare #3 it’s a prototype for the blackjack they made 3 of them. Jack had one Jack Jr. Had one and I have the only convertable. I also have a cobra f150 it’s a 97 with a cobra motor and a Kenny Bell blwzilla supercharger. I have paperwork on all.


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