I've long wondered about the "sum" of oddball FE parts that make up a GT500's motor:
Heads: same as 390GT including ports & valves
Exhaust Manifolds: same as 390GT Intake: C7ZX Med Riser it doesn't get any better
Exhaust System: I presume the same as a 390GT?...............
So when you have heads & ex-manifolds that are known to choke a 390GT, I'm guessing with nearly 40 more cubic inches of 428PI short-block it would only exacerbate the already restrictive components?..................The advised "shift-point" of 5,100rpm in the vintage road test to me makes sense if things are restricted here and there.
Below is a new Car & Driver article and a vintage road test of GT500 article, both linked
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CAR & DRIVER
A '67 Shelby Mustang GT500 and the Joy of Aimlessness
For the first time in years, I went for a drive without having to think about work. I had to retire to realize what I'd been missing.
The Salmon River. Fall colors. And a seven-liter Mustang. Life could be better—but only in the movies.
Owen bought the car 34 years ago, when he drove to a Mustang club convention in Calgary, Alberta. At that point, the car was filthy, faded, and—with 54,000 difficult miles on the clock—already a bit weary. The owner had paid $5200 for it new. Owen offered $7500. Some hand-wringing ensued, but eventually the seller countered with $7800 plus free delivery to Missoula. Since then, Owen, by himself, repainted the Shelby in its original colors—the stripes are paint, not tape—and has driven the thing 40,000 miles, including a trip to Las Vegas, where it was 105 degrees. No A/C, of course. “My wife and I wore our bathing suits,” he remembers.
Along the way, Owen met Carroll Shelby twice at club soirees in Vegas. When the GT500 was introduced, Shelby had said it was “the first car I’m really proud of.”
Ol’ Shel signed the underside of Owen’s passenger’s-side visor—“I couldn’t bear having him scrawl all over the dash, which always looks to me like vandalism”—and Owen was surprised that Shelby didn’t extend a palm for payment. At the time, Shelby was partly supporting himself—à la Pete Rose—selling autographs on everything from mud flaps to 1966 seven-liter Ford Galaxies, a copy of which, sans autograph, Owen also owns. “The man was a quick draw with a Sharpie,” Owen admitted. As Shelby walked away, he said to Owen, “I’ll never forget the boys from Montana.” It might have been a compliment. It might have been a threat.
When I climbed behind the wheel, I was transported back to the ’60s. I believe I began growing zits. The steering was so awful that it would have been rejected on WWII landing craft. But I owned a ’70 Mustang Boss 302 that was equally nautical. That a lot of folks herded these cars around racetracks strikes me now as semisuicidal. On the other hand, the GT500’s ride was surprisingly good. Plus, there was the familiar waft of unburned fuel in the cockpit; a seven-liter exhaust boom that made conversation tricky; a clutch pedal heavier than remedial trigonometry; an amount of wind noise that would have flustered the Wright brothers; and furnace-quality heat that flowed unimpeded through the firewall. My Orvis shirt was a mop in 30 minutes. On top of that, I believe I tried to shift into the nonexistent fifth gear maybe 200 times, which always made Owen clear his throat like Richard Nixon. Otherwise, he’s a lovely 56-year-old guy. I saw no goat glands.
Owen won’t enter his GT500 in concours events. “If a judge says to me, ‘Hey, you got a rock chip over here,’ I might try to kill him. I remind people, ‘Look, I drove the car here. See? No trailer.’ ” In fact, last Sunday we sent plenty of gravel flying, and Owen never flinched. “When I retire,” he told me, “I’ll make a two-year project of repainting it myself. In the meantime, I’m gonna beat the shit out of it.” What a sublime mantra for a car guy driving a Mustang worth at least $125,000. In fact, that night I saw a ’68 GT500 KR in Sports Car Market, same color as Owen’s. Asking price: $189,900.
I’m pretty sure the point of our drive was that there was no point. We just sloshed around in the car’s considerable aura as Owen described, among other wonders, his 1985 drunken dinner with Hunter S. Thompson. Oddly, I hadn’t gone for an aimless drive in, oh, about a decade. It’s not as if I didn’t have access to cool cars. It’s just that driving a car meant thinking about a car, which inevitably meant writing about a car, which meant work. I had to retire to realize what I’d been missing.
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http://www.caranddriver.com/columns/a-67-shelby-mustang-gt500-and-the-joy-of-aimlessness-column===================================================================
CAR & DRIVER MAY 1970
Seven liters! Four hundred and twenty-eight cubic inches in a Mustang! We were expecting a cataclysm on wheels, the automotive equivalent of the end of the earth. We were pleasantly surprised to discover that the GT 500 isn’t anything like that.
The old corollary to that old adage, “There’s no substitute for cubic inches,” is “except rectangular money”–and who would know better than Carroll Shelby. When the Cobra 289 peaked out on the racetrack, there were several ways of making it go faster–most expensive, one cheap. One of the more expensive ways was the Daytona coupe body. The late Ken Miles found a better way. At Sebring in 1964, he shoehorned a Ford 427 NASCARized engine into a Cobra roadster. The experiment came to rest, sorely bent, against a palm tree, but Miles persisted. By the end of the season, at Nassau, he had another one bolted together. It blew up, but the die was cast. Early in 1965, Shelby announced the Cobra II with a 427 cu. in. V-8 replacing the 289. That June, at Le Mans, two of Ford’s rear-engined GT prototypes appeared with the big 427 instead of the 289. The Europeans hooted and jeered at the bulky, heavy, unsophisticated V-8 with its pushrods and single four-barrel carburetor. A year later, Ford 427s swept the first three places at the French classic, with Shelby’s two entries dead-heating the final lap. What the 427s had beaten was a team of 270 cu. in. Ferrari V-12s with multiple carburetion and four overhead camshafts. The Italian engine developed almost as much horsepower as the Ford–425 hp vs. 485–but it was much more tautly stressed and, therefore, fragile. Which is the whole point of 7-liter Fords, Cobras, and now, Shelby Mustangs.
For '67, Ford offered the Mustang with their tried-and-true 390 V-8, which has a bore and stroke of 4.05 x 3. 78 inches. Ford also builds a 428 V-8 on the same block with a bore and stroke of 4.13 x 3.98 inches. Why not, reasoned Shelby, use this engine in the '67 Shelby Mustang? Why not indeed. The car is called the GT 500 and its engine is called the Cobra Le Mans.
VIEW 11 PHOTOS
Somebody is telling a little white half-truth.
Please note that the Cobra Le Mans engine displaces 428 cubic inches. That sounds like a hair better than the 427. In fact, they are two entirely different engines. Both have the same external dimensions, but the 427 is more oversquare, with a bore and stroke of 4.23 x 3. 78. The 427 is a racing engine, full of the kind of intestinal fortitude that makes it capable of enduring 500 miles at Daytona and 24 hours at Le Mans. The 428 is a passenger-car engine, and nearly $1000 cheaper than the 427. Few people would be happy with the 427 unless they were racing it. It’s noisy, balky, and an oil burner at normal highway speeds.
The GT 500 is not a racing car, although but for a few subtle differences its engine is the same as the one that propelled Shelby’s Fords to victory at Le Mans. Seven liters in a Mustang! The early GT 500 engineering prototype was the fastest car ever to lap Ford’s twisty handling loop, except for the GT 40s, of course. And the same car cut a quarter-mile in 13.6 seconds at 106 mph. Super car!
So we braced ourselves when we stuck our editorial foot into the first production GT 500. And when it only turned 15.0 at 95, we were a bit disappointed. That’s only 2/10ths of a second quicker than the Mustang 390 automatic (C/D, November '65) and last year’s GT 350H automatic (C/D, May '66), and not quite as fast as the original GT 350 4-speed (C/D, May '65). But then we thought back on the earlier GT 350s and realized that what the old Shelby Mustang does with difficulty, the GT 500 does easily.
The GT 500 is an adult sports car. Shelby’s Mustangs have come a long way in three years–from adolescence to maturity. The '65 GT 350 was a hot-rodder’s idea of a sports car–a rough-riding bronco that was as exciting to drive as a Maserati 300S, and about as marketable a proposition. The traction bars clanked, the side exhausts were deafening, the clutch was better than an advanced Charles Atlas program, and when the ratcheting-type limited-slip differential unlocked, it sounded like the rear axle had cracked in half. It rode like a Conestoga wagon and steered like a 1936 Reo chain-drive, solid-tire coal truck … and we loved it. It was a man's car in a world of increasingly effeminate ladies' carriages. You drove it brutally and it reacted brutally. Every minute at speed was like the chariot-racing scene in "Ben Hur."
Unfortunately for Shelby, the market for a car as hairy as this was limited. One state's motor vehicle bureau complained that the brakes, although virtually fade-proof, required too much pedal pressure. Apparently, the inspectors' leg muscles had atrophied from years of dainty stabs at over-boosted power brakes.
For 1966, Shelby toned the GT 350 down from a wild mustang to a merely high-strung thoroughbred. It was barely tame enough for the Hertz Corporation, which bought 1000 of them and put them into service as the hottest rent-a-cars the business has ever seen.
The GT 350 still wasn't acceptable to a large enough body of potential buyers, so, in 1967, an abrupt change in policy has transformed the Shelby Mustang. The $1000-or-so above the price of a comparable Mustang that used to go into expensive, unseen mechanical improvements is now lavished instead on exterior styling changes. The back lot at Shelby American's remanufacturing plant is littered with stock Mustang front and rear sheet metal, and engine and trunk lids. In their stead go fiberglass panels stylized by Ford's Chuck McHose, working in close co-operation with Shelby American.
The new nose piece arches tautly forward, forming a deep cowling for the headlights (changed from duals to quads, with the high-beams centered in the grille, driving-lamp style). The hood features an air scoop even larger than last year's, now divided by an air-splitter, and it's still functional. At the rear, the new trunk lid and tail piece combine to form a racy-looking aerodynamic spoiler lip. No one would say for sure if high-speed tests had proved the efficiency of this styling gimmick or not—but it looks right. Finally, the side louvres have been replaced by scoops—big hairy scoops that poke out into the airstream beyond the boundary layer. Actually, these are to let the air out; stale interior air exits through the inconspicuous slot behind the scoop. The forward facing scoop leads to a narrow venturi area that helps draw air out the rear slot. That light behind the scoop flashes when the turn signals are on and glows steadily when the brakes are on. Another pair of funnel scoops are installed at the rear of the sculptured side panel—this time to blow air at the rear brake drums. A pair of giant taillights running almost the full width of the Kamm-inspired tail completes the Shelby look. As a whole, the Shelby Mustangs make the regular Mustangs look sick.
Underneath, the Koni shock absorbers have given way to less expensive adjustable Gabriels; the traction bars are gone; the noisy racing differential has long since disappeared; and the Shelby Mustang has become a lot less like a NASCAR stocker without becoming any less roadable. The engineering is now built into stock parts instead of having to be included in extra hardware. Klaus Arning and the same computer he used in setting up the suspension of the Ford GT 40 and Shelby’s Cobra II determined the front suspension geometry, and the front anti-sway bar has been reduced from an almost immovable one inch to a more compliant .94 in. The rear leaf springs are now equipped with little rubber bumpers called "hopper stoppers" that are designed to prevent axle hop under hard acceleration. Most of the competition-bred racing equipment is still available—if necessary—as options. Oddly, the rear springs are stiffer this year (135 lbs./in. vs. 115 lbs./in. in '66), but the actual ride is smoother. 'The front springs of the GT 500, at 365 lbs./in., are naturally stronger than those of the GT 350, at 330 lbs./in.
We drove, briefly, a '67 GT 350, and noted how busy and mechanical the engine sounds. Jumping from that into the GT 500, the most marked difference was in engine noise, which is practically non-existent in the 428-engined car except for a motorboating exhaust throb. Our test car also had an automatic transmission (it will be difficult to get a GT 500 with a 4-speed manual), power brakes, fast-ratio power steering, air conditioner, shoulder harnesses and roll bar. (More about these last two items later.) All the viciousness had gone out of the car, without any lessening of its animal vitality. It still reacts positively, but to a much lighter touch. The power brakes, we felt, were a little oversensitive, but the automatic transmission was near-perfect. The GT 500 accelerates powerfully at any legal speed, gets off the mark with little wheelspin despite the absence of a limited-slip, and shifts very crisply. The automatic is a beefed-up Ford C-6, and each gear change feels like "a shift and a half," in the words of one staffer. The power steering is among the best we've driven, partially because it's quick, but mostly because we could actually feel the road through the wood rim wheel (standard equipment).
In softening the car to make it more acceptable to a wider market, some of the sheer handling virtuosity of the old GT 350s has been lost, but not much. As you might expect, the car understeers until you get the throttle open. It tracks well in a corner, and is exceptionally agile in evasive maneuverability tests for a 3500-lb. car. Our handling tests were made with 40 psi in the Goodyear Speedway E70-15 tires (similar to Firestone's Wide Ovals), so the harshness control was not all it would be with normal pressures (28 psi front and 24 psi rear).
The acceleration was not all it might have been either. With less than 100 miles on the odometer, the engine was tight and breathless at anything much over 5000 rpm. The redline is 6000, but we got the best acceleration times letting the automatic shift by itself at 5100 rpm. (Note open-rear)
The .74 G braking ability might have been better if the power brakes were more controllable. Wheel lockup was hard to avoid, and harder to correct—pedal pressure has to drop to near-zero before the locked wheel begins rolling again. This is a trait common to Ford power brake systems, and a better compromise between the touchy Dearborn system and the old GT 350 leg-buster could be worked out.
We're sure someone will utter a cry of protest, but to our knowledge, the '67 Shelby Mustang is the first production car to offer a true rollover bar as standard equipment. Not a thicker roof section, but a real live roll bar. The shoulder harness is not standard equipment, but like the GT 500's automatic transmission, it will be difficult to get a Shelby Mustang out of the showroom without one.
The roll bar itself is a tubular structure, covered with padding, and welded to the chassis. Where it curves up into the roof, tabs poke out, and bolts secure the bar to the car's top in the threaded holes intended for the upper attachment point for Ford's over-the-shoulder shoulder harness. Shelby's shoulder harness is the double type. Another pair of tabs are welded to the roll bar, and to these are bolted a pair of inertia reels made by Advanced Safety Devices. The reels exert a half-pound pull, thus requiring no adjustment by the user, and lock at .5 G, something like a window shade mechanism in reverse. The shoulder harness strap divides just behind the user's neck, the halves passing over his shoulders to fasten at points on either side of the seat. A standard lap belt is used in conjunction with the shoulder harness, but because the halves don't come together at the lap buckle, like racing harnesses, it's the only shoulder harness we've seen that women can wear. These devices have to be seen and felt in action to be believed. At the risk of encouraging showroom traffic by curiosity seekers, we'd recommend that our readers stop by Shelby American dealers and try the shoulder harnesses. Then, no matter what other car you may buy, drop a line to the manufacturer and suggest that he offer shoulder harnesses like this on his cars.
The rest of the GT 500 interior is stock Mustang, except for a few points. An oil cooler is standard equipment, but had been removed for some obscure evaluation on our test car, and an oil temperature gauge had been mounted under the dash. It never got over 230° F, incidentally. Our car also had the optional folding rear seat and an instrument cluster (ammeter and oil pressure gauge—the pressure was a steady 60 psi). The presence of the shoulder harnesses greatly complicated entry to the rear seat, what with climbing through a mass of nylon straps and ducking the inertia reels.
The air conditioner controls were confusing in an otherwise well laid-out interior, but this small annoyance was more than made up for by Shelby's special wood-rim steering wheel. It has much less dish than Ford's, thus placing it in a perfect position for effortless control.
That, then, is the GT 500. A grown-up sports car for smooth touring. No more wham-bam, thank-you-ma'am, just a purring, well controlled tiger. Like Shelby says, "This is the first car I'm really proud of." Right. We've come a long way since bib overalls too, Shel.
http://www.caranddriver.com/reviews/1967-ford-mustang-shelby-gt500-road-test
