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by Steve Temple  More from Author

Full Metal Jacket for a 500hp Big-Block Cobra

Shelby Cobras have been built in just about every possible permutation, from road-course racers to dragstrip duelers, powered by everything from Ford small-blocks to a twin-supercharged big-block. (Recall the Super Snake with dual Paxton blowers featured in our previous issue, which recently sold for $5.5 million.)

Just when we think it’s all been done before, somebody comes up with a new twist on the tale of the snake. Check out this Kirkham replica, for instance. Two differences are immediately evident at first glance: the elemental, bare-aluminum body and the removeable hardtop with a split-lid trunk.

Granted, we’ve seen unpainted aluminum Cobras before, but this one takes it to a new level of finish by using a special treatment from the aerospace industry (more about that shortly). And the LeMans hardtop has some historical basis, but not in a precise fashion.

According to Tom Kirkham of Kirkham Motorsports, originally this modification was used on an AC Cars Cobra raced at LeMans, but never offered on the 427 in the United States by Shelby American. “It was a good idea from one car moved to another,” he notes.

How so? Basically to improve on the Cobra roadster’s poor aerodynamics, which Carroll Shelby has compared to a “shoebox.” (Hence the need for designer Pete Brock to develop the wind-cheating Daytona Coupe that went on to win the World Manufacturers Championship.) Kirkham says a roadster with a hardtop runs as much as a half-second quicker per lap on the roadcourse at Goodwood in England.

No surprise, then, that this hardtop configuration appears on many roadsters replicas raced in Europe, but it’s still fairly rare here stateside. As of this writing, Kirkham has produced less than a half-dozen of them. At $15,000, this option is fairly pricey, but it does include the requisite split-trunk setup, along with enlarged side vents adjacent to the front wheel wells.

Tom Kirkham admits that it makes the car harder to get in and out of (since you can’t slide in from above the cockpit like most Cobra roadster owners normally would). And rearward visibility is reduced, but with a 500hp Roush aluminum V-8 under that shiny hood, you probably aren’t going to worry much about what’s behind you unless it’s a car with flashing red lights.

While Roush builds a comprehensive range of engines ranging from 327 to 588 cubes, up until recently there was a conspicuous absence in the lineup: a 500hp big block. Working in concert with Shelby American, Roush achieved this pivotal power output by punching out a 427 aluminum block to 451 cubes.

Freidman admits that the car is a handful with so much torque on tap. “It’s not a first-timer’s Cobra,” he warns. To give the engine some bling, he fabricated a custom billet coolant tank. The traditional Cobra puke tank hasn’t been made yet, but he’s working on it. Right now he’s just relishing that big-block power with small-block poundage.

The numerical value of the output is the same as the chassis number, which has some personal significance for the car’s owner, Darren Friedman of www.handcraftedcars.org. He’s built nine Cobras over the years, many of them groomed to a fare-thee-well, with every conceivable option and upgrade, and engines ranging from a 289 to a 460 Ford (following in the steps take by the original Shelbys, as noted above.)

This Kirkham, though, would take a different path. “I’ve won lots of awards with my other cars, but I’m done,” Friedman admits. “No more customizing—just stripped-down raw fun on this one.”

He means that in every sense of the term. Besides lacking such simple amenities as a radio and fuel gauge for the mammoth 40-gallon tank (which Cobra enthusiasts know aids the weight balance of the car), the aluminum body has just a simple skunk stripe down the middle, created by brushing the masked-off surface with a Scotch pad.

So how did Friedman achieve such a flawless finish? We’ve seen bare-metal Cobra bodies with a satin finish, and a few with a similar mirror surface, but nothing to this degree. Based on recommendations from Kirkham, Friedman used a compound and device employed by the aircraft industry to give a gleam to the exterior panels on jet liners. (While muscle cars typically don’t have an aluminum body, they do have other aluminum components that might benefit from this process. For details, see www.perfectpolish.com.) He admits the process was fairly time consuming, but the results were worth it.

Other buildup challenges included finding sufficient clearance for the air cleaner with the Edelbrock Victor Jr. manifold, which required modifying the hood and trimming the bottom plate of the air cleaner. He also found that a short-shaft TKO 600 tranny was required. Otherwise, the car went together smoothly, and the hardtop fits easily, and comes off even quicker.

As a side note, registering the car in California was a snap as well, which is not always the case in some states. For what it’s worth, the highway patrol officer who inspected the car said it was the nicest one he’d ever seen, but he did point out that he’d write a ticket for the non-DOT racing tires if he spotted Friedman on the street. Those Goodyear Eagles are actually racing tires that were custom-grooved with a V-tread.

Other specs on the car include a stainless steel, four-inch round tube ladder frame, and original-spec suspension modernized with Penske model 7500 coil-over shocks and Wilwood brakes with 1.250-inch Superlight rotors. Trigo supplied the 15-inch knockoff wheels (8.5 inches wide in the front, 9.5 in the rear).

So where does Friedman go from here, now that he’s built his final fantasy? Anywhere he wants, and he’ll get there quicker than just about any ride on the road.

Specifications:
Roush / Shelby Aluminum 451 FE
Power:  506 hp
Torque: 497 lb./ft.
Crankshaft: Scat Nodular Iron 3.980 Stroke
Pistons: Wiseco Forged Aluminum 4.250-inch Bore & 10.0:1 CR  with Plasma-Moly File Fit Rings
Camshaft:Roush proprietary Hydraulic Roller Camshaft & Lifters
Oil Pump: Melling High Volume
Radiator: Aluminum kirkham
Alternator: 100 Amp Single Wire Alternator
Heads: Edelbrock Aluminum
Induction: Holly 770 with Edelbrock RPM Dual Plane Intake Manifold
Ignition: MSD 6AL
Headers: Steel Kirkham Ceramic coated
Transmission: TKO 600 with short shaft
Flywheel: McCleod
Oil Pan: 8 Qt. Canton Fully Baffled Road Race

SOURCES:
www.handcraftedcars.org
www.roushperf.com
www.kirkhammotorsports.com

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