Reflections upon a supercar

1969 Shelby GT-350 (factory customized 1969 Ford Mustang)

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You'll enjoy a considerable headstart building your own Shadowfast if you begin with a 1969 Shelby GT-350

This page last updated on or about 3-24-15
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BACK to Me and my Shadow supercar: Project notes

It's been tough but fun to try recalling everything I could about Shadowfast, since I decided to divulge his existence to the world on the web in 2004.

There's definitely been some surprises along the way. For instance, I discovered that for all the independent design and effort I put into building my custom supercar, Shadowfast in the end was almost identical to a 1969 Shelby GT-350, innards-wise. I'm pretty sure that at the time I built him I was not aware of such close similarities.

If you don't believe me, look it up for yourself: Check out Shadow's specs here, and then do some Google searches for 1969 Shelby GT-350 specifications.

Reminder: Shadow began life as a 1969 Mustang Mach One, apparently with the options of an FMX auto trans and four barrel carb version of the 351 Windsor engine added in by the original dealer or buyer. If a four speed straight shift had been accepted instead, Shadow would have also gotten staggered rear shocks.

Now it turns out 1969 Shelby GT-350s were basically 1969 Mustang Mach Ones with a roll bar, staggered rear shocks, and the optional power front disc brakes added. Virtually all the other innards were identical to stock Mach Ones. So the Shelby apparently came stock with a C4 auto trans rather than FMX. It seems they also replaced the normal heavy intake manifold with an aluminum one (just as I did with Shadow).

Of course, guts alone aren't everything-- the Shelby's most obvious difference from the Mach One was cosmetic: maybe a full fiberglass front end, as well as some fiberglass mods to the side scoops and rear spoiler.

Replacing this much metal with fiberglass also helped the car's performance of course by lightening it.

There were some other nice touches on the Shelby, like a tilt steering wheel and racing harness for the driver, as well as real engine monitoring gauges in the console. But that fiberglass front end and rear touches seemed to have been the biggest differences by far.

If you'd prefer to see all of Shadowfast's technical details in ebook form, Dark Horse: The Official Shadowfast Supercar Technical Reference is now available for any Amazon Kindle or Kindle app.

So my advice today to anyone trying to build the nearest possible clone of Shadowfast is: Start with a 1969 Shelby GT-350. Hopefully equipped with the optional FMX auto trans.

Heck, on a couple items you'll actually be ahead of the game in your finished product here, with a racing harness for the driver and power front disc brakes. Those were both items I would have liked to have had for Shadow but never got around to installing (mostly for cost reasons).

But of course there'll still be lots more to do to build your own Shadowfast. It's just that beginning with a GT-350 will save you some work, such as staggering the rear shocks yourself, or adding in the main component of the roll cage. Or cutting out holes in the rear wheel wells to duct cooling air from the scoops to the rear brakes. Stuff like that.

Unfortunately there'll remain lots more to do, to get a GT-350 up to Shadow status.

Here's a list:

Beef up the GT-350's roll bar with another five components: In Shadow's specs page I describe all but two of these components. Here's the mysterious remaining two:

Basically they're just slightly bigger in diameter pipes than the main roll bar itself. Big enough so that the floor ends of the main bar snugly slid down inside them, maybe a foot deep. So these extra sections were sleeves. I welded the bottoms of the sleeves to Shadow, and then welded the main bar to the sleeves all around the top edges of the sleeves themselves. I guess I was wanting to make sure there could be no 'mouse trap' action ever occur with the roll bar in a crash. I spent much welding time on these main junctions, maybe laying more metal there than was really necessary. The effect of all this extra reinforcement in the center of the car seemed to be dramatic on its unibody construction. Basically '69 Mustangs posessed two small frames, one in the front and one in the back, and the two were tied together by the formed sheel metal comprising the remainder of the car. This meant the cars were weak or somewhat flexible in the middle. Shadow's roll cage changed all that though. The extra rigidity improved Shadow's handling still more. Plus strengthened Shadow to the point that he could survive jumps like those described in Nowhere to Go But Up.

In any real-life endurance test comprised of one or more 'Dukes of Hazzard' style extreme car jumps, I'd much rather trust in Shadow's roll cage and steel body than the Shelby's roll bar and fiberglass front end construction. Though I admit the Shelby's racing harness might have been very nice to have in such an instance.

Remove and throw away most all the fiberglass of the car (if any of it still remains after all these years). Yeah, I hate to say that-- as well as lose the weight reduction benefits-- but metal stops bullets better, plus can absorb much more punishment in general on the road and off. If you want to match the original Shadow you'll never do it with wholesale fiberglass use.

Of course if you're more into collectibles and car shows than real world supercar driving, you'd best keep any Shelby as stock as possible.

2005 TECHNOLOGY UPDATE: Note that 2005 car builders may have the option of rendering carbon composite body parts for Shadow, which may even be tougher than metal for such things like stopping bullets and bouncing back from some pretty rough and tumble driving conditions. In theory you could even remake the original Shelby fiberglass parts in this stuff and so make them more acceptable for real world use. But using the Shelby appearance would lose you the greater aerodynamic functionality Shadow's original design enjoys over the Shelby configurations. Of course this would matter little at low speeds and most at very high speeds. Personally I prefer Shadow's look to the Shelbys too, but that's probably just me. Retaining the Shelby look in parts would likely mean better collectible and show car value. There's another Gotcha! here though: the cost. It's still pretty expensive to fab stuff in carbon composite I believe. END UPDATE.

But getting back to the mods to upgrade a Shelby to a Shadowfast...

Acquire the appropriate metal body parts of both 1969 and 1970 Mustangs, front and rear, and heavily customize them to Shadow specs. Note that Shadow's rear wraparound spoiler was considerably larger and more functional than the Shelby's. And Shadow's air dam versus the Shelby's front end-- well, just examine various race tracks to see where and how often Shadow-like air dams are used compared to the characteristics of the Shelby's front end design.

Note that a tad of fiberglass work here and there is just fine, so long as the vast majority of the body is metal. A Shadow clone must be tough and able to shoulder its way through some pretty wild conditions.

The true source of this page is

Beef up the GT-350's suspension with a bigger front anti-sway bar and a rear bar too. Add traction bars. Did a 1970 Boss 302 Mustang have stiffer rear leaf springs than a 1969 Shelby? Maybe. If so, you'd need to use those to replace the Shelby's too. For that's what Shadow sported. I robbed all the best rear suspension stuff off a wrecked 1970 Boss 302 in a junk yard one day. The yard owner picked up the car end with a wrecker and held it suspended while I unbolted everything. CAUTION: Don't repeat my possible error here of inadequate safety precautions. I can't really remember if I propped some failsafe supports around just in case back then, and maybe I didn't. But if not and the wrecker cable snapped I would have been squashed. END CAUTION.

It seems Shadow would have left stock Shelbys in the dust in any extended cornering competition-- especially at higher speeds. For according to all the specs I've found the 1969 Shelbys had no rear anti-sway bar at all, and their front bars were smaller than Shadow's. Both Shadow's front and rear springs may also have been stiffer-- not to mention any effects from the traction bars. And the higher the competition speed the more the downward air pressure due to Shadow's superior air dam and rear spoiler would have come into play too.

Of course the above comparison may be a little unfair. For maximizing cornering ability was one of my greatest priorities on the car. I'm sure the Shelby designers were at least a little less concerned about it than I-- since I knew my life would be depending on it.

Add true headers to the engine. Maybe do away with any C4 or straight shift in the car in favor of an FMX trans, if practical. An auto trans is better than a straight shift in protecting your motor from being killed by violent maneuvering or abrupt stops. And an auto tranny will also help you out if you've got to rummage around for a weapon while on the run (like the flare gun incident in Nowhere to Go But Up). As for choosing the FMX over the C4, well, as the FMX appears to have been optional and the C4 standard at the time, it seems Ford themselves regarded the FMX as the better tranny. And my own FMX seemed indomitable in action. It took everything circumstances threw at it-- including my own dumb mistakes-- and never skipped a beat.

Definitely replace the Shelby's fuel tank with the two gallon bigger Mach One model. I'm unsure why, but '69 Shelbys seem to have been terrible in gas mileage (12-16 mpg) compared to Shadow (24 mpg), AND had a smaller tank to boot. This was despite the Shelbys being much lighter than stock Mach Ones by virtue of all their fiberglass, their carburetors sucking lots fewer CFM, and their engines (according to published specs) being virtually identical to what Shadow ended up having. So in driving range alone Shadow would have left Shelbys maybe hundreds of miles behind or further in an endurance competition.

Speaking of drivetrain efficiency, how did Shadow match up to stock Shelbys in the raw performance department? Well, though it may sound strange, despite Shadow beating the Shelbys hands-down in fuel efficiency, both cars ran neck and neck in straight-line quarter-mile times, based on everything I know today. I've seen quarter times with as little a difference between the designs as one-one hundredth of a second (the optional super-charged Shelbys being excluded from this comparison).

Of course this performance could likely be boosted by measures like replacing the original dual point distributors with electronic systems, or swapping out camshafts for hotter versions. Various head modifications might help too. Or for extreme boosts a nitrous oxide system could be added (but you must exercise caution there: nitrous can also blow an engine that's not in adequate condition, or where the nitrous is dialed up too much for the motor to handle). Turbo-chargers and super-chargers are also available, but a full-blown engine overhaul might be recommended as a prerequisite for those.

Personally I can't imagine ever needing much more power than a plain old Shadow or Shelby equipped with a nitrous system would offer the driver. And even the nitrous would be overkill for any circumstance a normal person is likely to find themselves in these days...unless of course you're a certified race car driver.

If your Shelby's got a fold down rear seat or is a two seater from the factory, maybe you can leave the interior alone-- unless it's too much in the way of building the roll cage, or reducing the car's weight like Shadow, or moving the battery into the passenger compartment for better weight distribution. The stock interior might also give you a problem regarding adding the overhead console. But it's your call on all that.

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Don't forget the stealth measures in Shadow. Most all these were directly opposite to the highly reflective stripes of Shelbys, as well as their shiny paint jobs. Of course, I'm NOT recommending you add the stealth lighting circuit listed in The Shadowfast Super Car Project, or even more radical devices described in Shadow's collection of unique gadgets and tricks. You'd probably get in trouble with the law if you did that. That stuff's dangerous, and best not tried at home-- or anywhere else!

For all my efforts with Shadow, I never managed to affect as big a net reduction in his total weight as I wanted. At least that's the impression in my fuzzy memories of the events now decades past. But maybe I was being too hard on myself back then. Especially considering the shoe-string budget I was operating under.

I ran across an item mentioning that Mach Ones had a 55 pound sound insulating package-- and I remember removing lots of pretty hefty stuff of this kind from the floorboards and elsewhere. Unfortunately most of my mods were likely a wash or neutral in weight effects. For instance the roll cage with its welds and the two main carpeted rear interior plywood boards with their hinged door panels probably roughly equaled the weight of the old back seats and heavy metal plates they replaced.

Likely the biggest net weight reductions included the removal of that sound insulation, the replacing of the stock dash with the GT-40 design, and the replacing of the heavy steel engine intake and exhaust manifolds with an aluminum intake and headers.

So what was Shadow's weight once complete? And what was that of both a stock 1969 Mach One and Shelby GT-350?

I've checked with a variety of sources here, and come up with a variety of answers. Unfortunately, if Shadow's final weight was recorded anywhere in my notes of the time I've been unable to locate it so far.

According to my sources, the Shelby weighed in as low as 2,723 pounds and as high as 3,600(!) The 3,600 figure came from only one source though and the 2,723 from several. Plus, if there were convertible Shelbys that year, they may well have been much heavier than the others.

The average Mustang Mach One weighed in at 3,485 pounds new.

We weighed Shadow once. On a truck scale. I couldn't do it personally, as the scale was located on the grounds of a canning factory where I was not an employee at the time. But my dad was. So he took it in for me.

I asked him recently if he remembered doing that, and as expected his recall was pretty fuzzy. It was a long long time ago, after all. But he told me that the first number that came to him when I asked was "2,800 pounds". Yikes! That's a great number, if it's accurate! And no, I didn't prompt him for any specific number here. Actually, I didn't even ask for a number at all: I merely asked him if he remembered driving my car in to be weighed-- that's it. The number was his own spontaneous response.

I seem to recall dad handing me an official ticket at the time which may have had the weight printed on it...maybe I can find that someday. But I already did a major sifting of all my surviving papers regarding Shadow in order to write the 2004 presentation for him on the web. I'm sure I'd have seized upon any weight ticket had I come across it.

Above can be seen a Texas inspection ticket stating Shadow's weight as 2900 pounds. Note this was without occupants but almost certainly including at minimum 100 pounds of tools, gadgets, and spare parts in the trunk and other storage spots. I've blacked out certain info here that I consider privacy sensitive.

7-6-05 UPDATE: Eureka! In my ongoing efforts to harvest more details about Shadow from old papers I ran across an inspection ticket from Texas which indicates they weighed him(!) Huh? I sure don't remember that! Is it possible the service station hydraulic lift somehow gave such a measurement when they were inspecting his underside? I have no idea. But the ticket implies some sort of weight gauge was used. END UPDATE.

But let's put that 2900 pound or less vehicle weight into better perspective, shall we? And what better way than to compare Shadow's weight to that of state-of-the-art 2015 whopping expensive supercars, equipped with all the better performing lightweight materials and technologies money can buy, nearly four decades after I completed Shadow's own shade tree modifications: in particular, let's examine the 'super lightweight' supercars of 2015, such as the $2.3 million Aston Martin Vulcan, weighing in at 2,976 pounds, which according to the article set "...a whole new standard in the ultrahigh luxury supercar class."

That carbon fiber bodied $2.3 million Aston Martin Vulcan weighed 76 pounds MORE than Shadowfast-- if Shadow was also toting 100 pounds of tools and spare parts in his trunk. Or 176 pounds more than Shadow, if the tools and parts were left out. And Shadow cost only several thousand dollars to build.

-- Super Lightweight Supercars Dominate at Geneva Motor Show by Hannah Elliott, March 4, 2015

If you'd prefer to see all of Shadowfast's technical details in ebook form, Dark Horse: The Official Shadowfast Supercar Technical Reference is now available for any Amazon Kindle or Kindle app.

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