Dale Amy
February 1, 2004
Horse Sense: We'd love to get the Boss 351 on a road course. It has morepower--and apparently better weight distribution--than the vaunted '00Cobra R. How much fun would that be?

"Whaddya wanna do today?"

"Oh, I don't know. Why don't we whip up an all-aluminum, short-deck, modular V-10, stick it in a Mustang, and call up those boneheads at the car magazines?"

"Sounds good. I was gettin' a little bored."

This is most assuredly not how the project began for the talented enthusiasts at Ford Motor Company's Powertrain Research & Advanced Engines division (they never even thought of us magazine boneheads), and they are never bored with this kind of hardware around. But it does make one wonder just how such a seemingly unlikely bit of vehicular R&D ever saw the light of day.

This amazing spectacle is run like two inlinefive-cylinders by twin EEC V processors.

Had someone whispered to us even a few months ago that there was a New-Edge GT running around Detroit, wearing manufacturer's plates, and packing a DOHC 10-cylinder underhood, we would have laughingly dismissed the suggestion as fume-induced gearhead fantasy. Well, it turns out this thing has been unceremoniously prowling the streets of Motor City for more than a year now, proving once again that we should never be close-minded in this occasionally madcap business.

First, let's be clear that the 5.8 V-10 that is the centerpiece of this story has absolutely nothing in common with the cast-iron, tall-deck 6.8 10-banger found in Super Duty pickups and Excursions. Instead, this is an all-new engine that is most accurately visualized as a 4.6 Cobra short-block with two additional cylinders grafted on, and topped by similarly stretched Cobra R DOHC heads, resulting in an all-aluminum V-10 of surprisingly compact external dimensions and manageable weight. To be specific, it is some 60 pounds lighter than the 5.4 engine found in the '00 Cobra R. By adding the 25-percent displacement increase of two extra pots onto a 281, you get 351 ci. Therefore, it was only natural that the '99 GT it was strapped into should come to be known, in-house, as the Boss 351. Besides, the decals that emblazoned the '71 original of the same name were a cheap purchase, fitting nicely within the project's skinflint budget.

Indeed, the budget was so tiny, at least by Big Three standards, that it was described to us as a CCP--a credit card project--with most of the time spent in accomplishing it coming after regular business hours, or in the spare time of the can-do crew at Powertrain Research & Advanced Engines. You see, it was these guys who initiated the idea in the first place. They developed it on their own time as a project, researching possible means of providing a displacement increase to the short-deck 4.6 for applications where the taller deck (and subsequent increased width) of the 5.4 or 6.8 won't easily fit.

By adding the 25-percent displacement increase of two extra pots onto a281, you get 351 ci.

You won't find much argument around here that the little 281 could use a few more cubes. Because a major bore increase is not possible due to the modular's extremely tight cylinder spacing, it seemed a practical experiment, they reasoned, to gain that extra displacement by cobbling together a V-10, especially since this same compact bore spacing would result in an increase of less than 4 inches (100 mm, to be exact) in overall engine length. And to help, uh, expedite matters, they decided to go ahead and build one and tell their corporate bosses about it afterward.

Unlikely as it sounds, these professional tinkerers got underway by cutting apart some existing 4.6 V-8 sand-casting cores and literally gluing them back together in V-10 form. They repeated this cutting-and-pasting process on Cobra R head cores, poured in some molten aluminum, and--voila--they had their basic castings. In comparison to having all-new tooling made up, this process was incredibly cost-effective. They calculated that 5.4 Cobra R cam specs should be fairly close, so they had new, longer billet bumpsticks made in that grind. And, since they had stuck with the stock 4.6 bore and stroke, they were able to use Terminator Cobra H-beam rods, connected to pistons of about 10:1 compression that they "had lying around from another project."

The Cobra R hood looks cool, but it isn't a requirement for aV-10 Mustang.

The billet crank spun by those slugs is an interesting piece, again bearing no resemblance to the one in the truck 6.8 V-10. We'll let V-10 project lead Kevin Byrd describe it. "The 6.8 truck crank is a split-pin crank, like you'd find in a 60-degree V-6. [For the 5.8 V-10] we went to a common-pin design based off the Cobra crank, only instead of four pins, we have five. The crank is set at a 72-degree pin offset, but when you put that in a 90-degree block, it doesn't line up to a 72-degree firing. It ends up to be a 90/54, so you get that odd-fire sound, but it blends together beautifully."

We agree that the sound is both appealing and distinctive, unlikely to be mistaken for any old V-8, even though in the Boss 351 it's thoroughly muffled with four mufflers, along with two metallic and two ceramic catalytic converters. In one of the more challenging aspects of construction, five-into-three-into-one headers were bent up with no particular emphasis on performance, rather just something that would fit (using a tubular K-member made it all possible and took further weight off the nose).

The Boss 351 is set up to be at home on the roadcourse too.

Because of the common-pin, odd-fire crankshaft, the project crew couldn't just wire it all up to a single EEC V from the 6.8 V-10 (an engine that uses a split-pin, even-fire crank with balance shaft). Instead, they had to use two such processors, each one calibrated to think it's controlling an inline five and not knowing the other one exists. This requires duplicate crank, cam, mass-air, and other sensors, and it also necessitates the pair of 70mm throttle bodies that feed into the impressive-looking, black intake-plenum chambers. Through custom runners, these supply a lower intake that is a narrowed (that cut-and paste-thing again) Cobra R casting.

Carrying on with the miniscule budget theme, with the engine assembled--but never once tested on the engine dyno--it was decided to shoe-horn it into a well-used silver '99 GT unibody that had previously seen duty as the test-fit mule for a prototype '00 Cobra R 5.4 (explaining its bulging R hood, which is not needed to clear the short-deck V-10). We suppose the thinking was that if they could squeeze the V-10 into a Mustang, it would fit into practically anything. This job of wrapping the car around the engine fell to powertrain systems supervisor Jim O'Neill, and it turned out to be easier than you might think. Far as we know, he never even reached for a sledgehammer. Engine-to-firewall spacing remains identical to a production 4.6, and the additional 4 inches of length up front is, surprisingly, easily accommodated in the Mustang engine bay (all you state troopers out there, imagine how well this thing would fit in a Crown Vic Police Interceptor).

Knowing it was destined for a hard life of trying to convince management of its merits, the V-10 was backed up with a T56 six-speed and a 9-inch rearend (currently outfitted with 3.82 gears). As with so many others, these were pieces the crew was able to scavenge off the shelves of the Powertrain Research & Advanced Engines garage. A bit more calibration fiddling made it pleasantly driveable, and they eventually rumbled over to the Dynojet at Livernois Engineering to see what kind of power their little 10-pot dictator wielded. The project immediately proved its worth with 426 hp at 6,500 rpm and a nice, even 400 lb-ft of torque at 5,200.

"The whole car," Kevin Byrd summarizes, "was a process of a handful of guys just being as absolutely creative as possible, from making it, to making it run, and scrounging parts."

Jim was able to get the Boss 351 to Ford's Dearborn proving grounds andmake an 11.93-second pass at 117 mph.

Our Plan

Once the car went public, we hooked up with the folks behind the V-10 project, thanks to modular racer John Tymensky, who supports his quarter-mile hobby with employment as a Ford engineer. Our plan to wring it out for you was good, but--as is often the case--time turned out to be our enemy. We wanted to meet with the Boss 351 out at Milan Dragway's freshly refurbished quarter-mile, west of Detroit, and dip it well down into the 11s--something which, if its previously posted 123-mph trap speeds are any indication, the car should be easily capable of, at least if given the right amount of traction. Good intentions, of course, sometimes go astray.

After some on-again, off-again phone negotiation, we managed to get into Milan (thanks to the generosity of the folks at Visteon, who had the track rented for the day for their employees and allowed us to slip in). This was our first face-to-face encounter with the Boss, which has an oh-so- subtle outward appearance guaranteed to draw little attention. Lift the Cobra R hood, however, and that situation soon changes as bystanders are drawn like hummingbirds to nectar.

The first pass of the day was made with yours truly strapped into the passenger seat like some unwitting test dummy (for whatever reasons, Ford was not about to relinquish driving duties to anyone other than a corporate employee). After assuring track officials he wouldn't make any sub-12-second passes with a passenger, Jim O'Neill--who had played such a large role in the car's construction--blasted off, and, true to his word, let off at about the 1,000-foot mark. We coasted through the beams to a high-12-second performance. My first impressions? This is a Mustang that runs as if it has a Saturn booster secreted away in the trunk--and where do we get one? It pulls at least as well as a stroked blower car, but with no waiting for boost since torque is plentiful and is fully on duty at low rpm. It exhibits the grunt of a big-block, but, because of the deep-breathing Four-Valve heads and R cams, it also keeps on pulling all the way to its 6,800-rpm rev limiter.

I then stepped out and grabbed the camera as Jim made a couple more passes to try and find a combination of launch rpm and tire pressure that wouldn't overwhelm the car's worn drag radials. These passes were in the mid 12s, and things were looking up, right until the gutsy V-10 put a sudden and terminal hurt on its Cobra R clutch--its seventh, by the way--thus ending our brief day at the track and temporarily spoiling our 11-second plans. It was all we could do to limp the car around for some stationary photography. It was kind of sad, really, much like watching a wounded lion. But the lion recovered the next day, with clutch number eight bolted up, and with the repair of catalytic-converter media that had somehow twisted sideways in its canister, effectively corking the exhaust. Unfortunately, there was no more track time--or my time--available. Deadlines are such a pain.

The good news is, a few days after we left, Jim was able to get the Boss 351 to Ford's Dearborn proving grounds and make an 11.93-second pass at 117 mph, with a best 60-foot time of 1.83 seconds. He asserts--and we agree--that there's much more potential in the car. A decent pair of slicks would have this thing running mid 11s all day long--or at least until the clutch or some other drivetrain component gave out.

Ford's Plan

Where does the V-10 project go from here? Predictably, no one's talking, but it was "an extremely bored and stroked" version of this engine combination that showed up in last year's "427" concept car. Ford's a big company, and who knows which--if any--of its divisions might be looking favorably toward the idea of short-deck, 10-cylinder production applications.

Whatever happens, we can all sleep better at night knowing there are guys with this kind of passion and determination toiling away at the heart of Ford Motor Company. We can only hope that the corporate brass see merit in what they've accomplished on such a shoestring budget. Of course, none of this is to suggest we might expect to see a V-10 in a production Mustang anytime soon. Or is it?

138_0402_z 1999_Ford_Mustang_Boss_351 Rear_View0
The Boss 351 decals appear oddly at home on this V-10 '99GT.
138_0402_s 1999_Ford_Mustang_Boss_351 Front_End0138_0402_z 1999_Ford_Mustang_Boss_351 Interior138_0402_z 1999_Ford_Mustang_Boss_351 Gauges138_0402_z 1999_Ford_Mustang_Boss_351 Computer