The Shelby American (Fall 2021)

adding a hatch on the right side of the engine compartment to get at the oil filler pipe and dipstick, and installing a pressure filling system for the radi- ator, like NASCAR stockers. Having taken care of these primary considerations, the Shelby organiza- tion found they had come full circle: the weak point on the car was once again the gearbox. Until now, it had been a Colotti Type 37, a four-speed non-synchro transaxle unit. For Day- tona, Ford cut their own helical ring and pinion set, with a 10° helix angle, to replace the Colotti straight-cut gears. Ford also made 20 other changes and supplied tubular half- shafts to eliminate the Metalastik cou- plings. During the race, the team drivers babied the transmission. Ginther and Bondurant used low gear in their car; Miles and Ruby did not. Miles said the transmission is his GT, “could have done another twelve hours,” but low gear in the other car had been chewed up and the pieces were clogging up the rest of the gears. Obviously, the Colotti will be retired as soon as a substitute can be found. The best bet for now is the new ZF 5- speed. A ZF is being fitted to the car Wyer will manage in Europe and should have its first public outing at the LeMans test day in mid-April. The “ZED-F” box has had trouble with the needle bearings on the main shaft in bench tests, which has held up deliv- ery while it was being corrected. As- suming all goes well, one of Shelby’s cars should have a ZF for the 24-hour race. Handily enough, this brings us to a discussion of the future of the GT40, and of the new components being de- signed for it—transmissions, engines, body, etc. The first order of business, of course, the automatic transmission. “There’s no question about it,” says Miles, “the automatic box—with manual over- ride—is the way to go. What you need is a small torque converter, efficient at high revs, but inefficient at low engine speed where torsional vibrations are rather high. This sort of fluid coupling would take some of the load-unload shock out of the drive.” Ginther agrees: “It would be the smartest thing anybody could do—especially for the long distance races.” Ford will doubtlessly want to list the automatic as an option for the GT car on the homologation papers, thus the specifications for it may be an- nounced at the same time production plans are announced—hopefully by June—whether or not the car has ac- tually raced with the new transmis- sion. It’s also probable that new engines will be offered to take advantage of the stronger gearbox. As powerful as the car is now, Shelby would like to see it still more so. So would Ginther: “It could use more power. Definitely. The 4-cam Ferrari could just run past us on the straight at Daytona. For en- durance racing, it wouldn’t be neces- sary to have more power throughout the range—just at the top. If we could ‘cruise’ comfortably at over 200 miles per hour on the Mulsanne Straight at LeMans, for example, we could be very careful with the car elsewhere around the circuit and still have lap times that would win the race.” Some of that speed may be found in new nose shapes, but more likely it will come from hotter engines. The current engine puts out 385 b.h.p. at 7000 rpm and 312 lbs/ft. of torque at 5000 rpm. There’s also a “high torque” engine with less peak power but 342 lbs/ft. of torque (also at 5000 rpm) that’s used for circuits like Sebring and the Targa. “The 289 is by no means at the end of it’s tether,” said Miles. “We’re work- ing on a couple of projects that will bring the power up another 30 or 40 horses, still with 4.7-liter displace- ment. It’s no secret that we’re working on aluminum heads for the engine.” These heads, being developed in Eng- land and Italy, feature much-improved breathing, though still incorporating rocker shafts, not the bathtub rocker arrangement used in the “porcupine head” Chevy 396. “There are other en- gines in the offing—out and out racing engines—but nothing has been final- ized as of now.” Apparently the 4-cam Ford Indy en- gine is no longer being considered, al- though it will fit in the GT40 if the heads are reversed and the sill modi- fied to clear the exhaust pipes. Equipped withWebers, a 4-cam engine was in the car at one time, in England, but Ford called up and said they needed their engine back. Since then, interest in using the 4-cam has waned. For one thing, it costs a mint ($15,000). For another, as Lunn points out, there is no displacement limit on GT cars or GT prototypes, while the Indy engine was developed against a 4.2-liter maximum. “We feel we can do better by using volume to get horse- power than by squeezing a lot of horse- power out of a small displacement engine.” Using a 3/8-in. stroker crank, the 289 can be taken out to 327 cubic inches—about the limit for the Fair- line’s block. At that, the short connect- ing rod (5.155 inches center-to-center, vs. the Chevy 327’s 5.7 inches) have such a high angularity that they tend to drive the piston into the cylinder wall. Some new pistons are being made up, with the wrist pin practically sitting in the dome, so that rods with a longer center-to-center distance can be used, giving less angularity. Gurney went flat-out for 8 hours with a Cobra 327 (called the “325” for “325/327”, presumably to avoid sounding like a Chevy), so its reliability is improving each time out. Shelby told us, “You’ll probably settle on the 325—that seems to be about the kind of horse- power we’re looking for, the kind of power we can apply with our present chassis development and tire configu- ration.” The production of the GT40, using this engine with aluminum heads, would have over 450 horse- power on tap, which ought to hold off the Ferraris for a year or so. For the fu- ture, there is the 427 cu. in. push rod engine (the single cam 427 won’t fit without major alterations and proba- bly isn’t needed). With the aluminum heads from the Cobra 427, the big en- gine weighs only about 100-125 lbs. more than the cast-iron 289. The min- imum weight for a 7-liter GT proto- type is 2310 lbs., or 295 lbs. more than the maximum weight for a 4.2-liter The SHELBY AMERICAN Fall 2021 59