The job of putting together a "race car" Camaro program to beat Mustang went to Vince Piggins, head of Chevrolet Product Promotions. Within Detroit's super-heated competitive environment, the timing and venue couldn't have been better, and the SCCA provided its new "Trans-Am" Group 2 sedan-racing series. Although Chrysler backed Bob Tullius and his Dodge Dart competed early on, it was Piggins and his cross-town competitors at Ford who knew it wouldn't take long for the Trans-Am to heat up into a classic Chevy versus Ford battle. "We had reasons to believe," recalls Chevrolet Chassis Engineer Paul King, "that the Camaro would be very competitive in that series, and that sales advantage would be worth the cost of development."
Ford jumped in first with a back-door team of two Mustangs assembled by Shelby-American, and funded a Cougar effort headed by Parnelli Jones and Dan Gurney. With that kind of head start, it was no surprise the Mustang and Cougar teams shared 8 of the 11 victories in the 1966 series.
But Piggins saw "wham slam" Trans-Am racing as the perfect arena in which to prove the Camaro's superiority over the Mustang and Cougar. Even before the new Camaro was released to the public in September 1966, Piggins was savvy enough to make sure SCCA officials were aware of Chevrolet's intentions to go racing, and that they helped define the series specifications. He was also able to commit engineering and parts assistance to the teams that raced the Camaro, even though "Chevrolet did not participate in racing."
The Heart Of The BeastFirst, Piggins had to homologate an engine that came in under the Trans-Am displacement limit of 305 ci. Chevrolet offered the 283 and the 327 in their engine lineup, but nothing in between. The 283 wasn't stout enough and the 327 was too large, but Piggins deduced that mating the 4-inch bore of the 327 with the 3-inch stroke of the 283 provided a displacement of 302.4 ci. This was a tried and true combination racers had used before, and it met the SCCA's legal 305ci ceiling. It also meant that the 302 would inherit the intrinsic benefits of having a short stroke with an oversquare bore. A short-stroke engine can run at higher rpm for longer periods, since there is less piston speed. This is, of course, what a race engine has to do-run for sustained durations at high engine speed.
The small-journal, cast-iron block for the 302 was also shared with the 327 and 350 engines in 1967. The crankshafts were forged steel and Tuftrided for high-rpm durability. The rods were shot-peened and mated to 11.0:1 domed aluminum pistons with notched valve relieves. The iron heads featured big 2.02-inch intake, and 1.60-inch exhaust valves with wide passages and generous ports, to accentuate mid- and high-end horsepower response. The 302's "30/30" camshaft was lifted from the 375hp Corvette 327 fuelie engine, and designed for use with solid lifters.
A big 800-cfm, double-pumper Holley carburetor was bolted to a tuned-runner, dual-plane aluminum intake manifold, with the front crossover tapped for a temperature sensor. Log-style iron exhaust manifolds were standard with optional headers, and a single-point Delco-Remy ignition came standard with an optional transistorized ignition. Chevrolet blatantly underrated the 302's horsepower at 290 and torque at an equally silly 290 lbs-ft. In reality, the production engines generated more than 375 hp, with power coming on strong from 3,500 to 6,500 rpm, and still pulling at 7,000 rpm.
Selling The IdeaPiggins' concept of using off-the-shelf, high-performance components to build both a spirited performance street engine and a wicked race engine had another advantage: Chevy could come to market with a production engine using off-the-shelf parts at significant cost savings. This made it much easier to sell the program to Chevrolet management.
Chevrolet Engineering and Product Planning assembled the rest of the package, which Piggins referred to as "The Cheetah." Air conditioning and automatic transmission were not offered, and due to body rigidity problems, engineering decided against a convertible version. The 302 was to be mated to a four-speed Muncie manual gear box, heavy-duty F41 suspension, power-assisted front disc brakes with sintered metallic drums in the rear, fast ratio steering, and a cold-air induction plenum.
Piggins took Chevrolet General Manager Pete Estes for a demonstration drive at GM's Milford Proving Grounds outside of Detroit in October 1966. Piggins was a capable performance driver, and it didn't take him long to convince Estes to approve the project. "Estes was the driving force behind the Z/28," remembers Chief Engineer Alex Mair. In fact, he was actually the unsung hero behind many of the great performance cars that came from both Pontiac and Chevrolet in the 1960s, including the Pontiac GTO.
The Z/28 Is BornTagged as the next RPO after the Z27 SS Camaro Super Sport option package, the 302 Special Performance Equipment Option was designated Z/28 (this was also quickly accepted as the model name for the new race-oriented Camaro). The Z/28 was released to the press for first driving impressions at Riverside Raceway in November 1966. Chevrolet hyped the new Camaro by saying, "The Z/28 package was developed to make the Camaro an exceptional touring machine, having relatively light weight, a smaller but highly responsive V-8 engine with four-speed transmission, and suspension refinements that result in excellent stability and handling characteristics." Available, but not part of the Z/28 package, was a rear deck spoiler developed by Chevrolet Research and Development Engineer Paul Van Valkenburg and styled by Larry Shinoda.
The base Z/28 package cost $328.10, and included the 302-ci engine, 3.73.1 rear axle, dual exhausts, and 15x6 stamped steel wheels on 7.35x14 nylon redline tires. Heavy-duty suspension, heavy-duty radiator, and special wide stripes were also part of the package. There were three additional Z/28 packages, all built upon the base option. The Z/282 option cost $437.10, and included the Z/28 package plus a cowl-induction plenum/air-cleaner assembly, delivered loose in the trunk to be installed by the dealer. The Z/283 package for $779.40 added a set of exhaust headers, and was also delivered loose for dealer installation. The Z/284 included all the of above packages, for $858.40. A four-speed manual gearbox was a mandatory option, and was available in close- or wide-ratio configurations. Power-assisted front disc brakes with rear drum brakes were another mandatory option.
Build-Out & HomologationProduction of the 1967 Z/28 ramped up slowly, beginning on December 29, 1966. A handful of cars were delivered in early-January to dealers like Yenko, Nickey, and Dana, for preparation to race in the Trans-Am sedan series, as well as other venues. These first cars were built for racers-no radio, heater, or body sound deadener-and not intended for the general public. Many of the 602 Z/28s built in 1967 also included the Rally Sport option, although it was not mandatory. Chevrolet was supposed to produce 1,000 Z/28s to meet SCCA/FIA homologation rules; however, it found a way around that by homologating the SS350 under FIA Group 1 rules, then qualifying the Z/28 option under Group 2 rules. One of the reasons only 602 Z/28s were sold was a complete lack of marketing support from Chevrolet. Many dealers had no idea what a Z/28 was, and it wasn't pushed by the zone sales managers. Those who wanted to go sedan racing knew what Z/28 stood for, though, and found a dealer who would order one.
The Z/28 package was an enormous improvement upon the Camaro; however, cornering and braking agility was still dampened by its Achilles' heel-the mono-plate leaf rear suspension. Car and Driver noted that under heavy acceleration, "reaction to the engine's torque tips the car counterclockwise, unloading the right rear wheel. If the right side of the axle isn't tied down, it goes haywire." C&D also noted, "under heavy braking, the torque is coming from the opposite direction and the left side of the axle judders violently."
What's important to remember about the Z/28 is how unique its mission was. While the rest of the Camaro lineup was designed and built around standard street car parameters (a trait Car and Driver referred to as "a polished lack of character"), the Z/28 was produced to homologate a race car package; the parts selected fell within higher specifications not usually used by Detroit carmakers. By doing so, Chevrolet, unwittingly or not, came close to building one of the best American sports sedans ever made. "With the Z/28," Car and Driver observed, "Chevy is on the way toward making the gutsy stormer the Camaro should have been in the first place."
Jerry Titus, editor of Sports Car Graphic and a competent race driver himself, summed it best when he observed, "Where the Z/28 is significant is in the breakthrough of the stubborn policy to hold back options and hardware that would enable customers to be more competitive."
Jerry also knew that Chevorlet wouldn't provide factory-racing support. "It looks," he wrote in Sports Car Graphic, (Mar. '67), "like Camaro competitors may have to depend on prize money for support. Yet the vehicle itself will give them a fair shot at it, and that, after all, is the name of the game."
Struggling On TrackChevrolet was anxious to get the Z/28 on the track against the Mustang, and Piggins had already arranged with Roger Penske to build a two-car team. Penske had a long relationship with Chevrolet, racing Corvettes at Daytona and Sebring, and Chevy-powered Lolas in the Cam Am series, so he and Mark Donohue put together a development and driving team. George Wintersteen picked up one of the first production Z/28s at the Norwood assembly plant, and drove it to Penske's facility near Philadelphia. The red-with-black-stripes Z/28 had no radio, heater, or body insulation, and so Donohue and mechanic Bill Mayberry began tearing it down while Traco put together the engine.
As the Trans-Am series progressed, Donohue struggled to dial-in the Camaro's suspension and braking needs, and after four races, Piggins reluctantly realized that Donohue needed help finding the handle. Piggins and Corvette engineers like Gib Hufstader and Dick Rider attacked the braking and suspension problems, going so far as to bring the car to GM's Milford Proving Grounds for a covert battery of tests (including aerodynamics, spring combinations, and more brake work). It was obvious to Piggins and Chevrolet management that their help was essential if the Z/28 was going to beat the factory-backed Mustangs and win the Trans-Am series.
By the end of the season, Chevrolet engineers including Jim Musser found the right suspension and brake geometry, and Donohue began to win races. Penske built a second car-a lighter version that boasted acid-dipped body panels. While that car was under construction, their first car was heavily damaged in an accident while being transported to California, so the lightweight car had to be hurried to completion. Although it made it to the Modesto race, an incorrect rear axle gear stymied its Third Place performance.
The first car was rebuilt and campaigned along with the lightweight car; however, Chevrolet's resolve to continue supplying Donohue with engineering assistance and parts was waning. The Ford and Cougar teams were wailing on the Z/28, and there was little Chrysler could do to remain competitive. As Van Valkenburg notes in Chevrolet = Racing, "Politics and personalities were clashing behind the scenes at Chevrolet. Management was upset about the Camaro/Mustang showing in the Trans-Am, and the engineers were explaining that they couldn't solve the problems by telepathy." Since Chevrolet prohibited overt factory support, engineers couldn't have a high profile at races. "All their sophisticated tools and instrumentation," he wrote, "would be too obvious at any race track, and no one wanted to be responsible for allowing Penske's cars on GM facilities."
Fortunately, Piggins and Chevrolet engineering hung in with Donohue, finding ways to covertly appear at tracks and provide assistance. As the season drew to a close, the results began to pay off. The suspension was now dialed-in and responsive, the severe brake fading was solved, and the Traco 302 engine was delivering 420 reliable horsepower. In fact, Penske's Camaros won the last two events of the 1967 Trans-Am season at Las Vegas, Nevada and Kent, Washington. As the season ended, the record showed one win for Chrysler, three for Camaro, and four each for Ford and Cougar. Penske and Donohue's team found the handle, and would go on to win the 1968 and 1969 Trans-Am Championship.
Trans Am: Chevrolet's Back Door R&D DepartmentChevrolet didn't spend time and money helping Mark Donohue to correct the Camaro's inherent cornering and brake faults without some payback: they were able to capture and use the electronic data gathered during testing at Milford, as well as several other races in which Chevrolet engineers appeared incognito.
Along with applying some of the knowledge learned while improving production Camaros, Chevrolet Engineering built a test car using tricks learned from the Penske race car. As Van Valkenburg recalls in Chevrolet = Racing: "Its suspension was much stiffer than production, and at various times it ran with dozens of different combinations of springs, shocks, antiroll bars, optional geometry, and competition tires."
Perhaps the most significant spin-off of this research was the construction and testing of an independent rear suspension for the Camaro. Testing showed that in most cases in which the IRS borrowed from the Corvette, it barely out-performed the standard leaf-spring rear suspension. Ultimately, it was too expensive to tool for the Camaro, and was dropped.