Few automotive battles raged as fiercely as the “Ponycar Wars” of the 1960s. Ford’s Mustang launched a new market for personal sporty cars in 1964½, forcing GM to react with its Chevrolet Camaro in 1967. These two competed head to head in showrooms, stoplight matchups, dragstrips and road courses. And while the 35-year battle ended when GM retired the Camaro in 2002, the skirmishes these two competitors
fought reverberate today.
The most intense of these battles were conducted on the road courses of America and Canada in the Sports Car Club of America’s Trans-Am series. Introduced in 1966, the Trans-Am was open to four-passenger production sedans in two classes—2.0L and under and 2.0L to 5.0L. Ford commissioned Carroll Shelby to prepare a team of Mustangs for the first season’s competition against the Dodge Darts and Plymouth Barracudas running in the over 2.0L class. The Trans-Am series captured more than a passing interest with race fans and the automotive press, an impressive achievement for a first-year race series.
Watching with keen interest from the sidelines was Chevrolet’s Vince Piggins, one of the driving forces behind Chevrolet’s high-performance program. Before the first production ’67 Camaro was built at GM’s Norwood, Ohio, assembly plant, Piggins had already conspired with the SCCA to bring Chevrolet into the Trans-Am series, developing a special package for homologation.
Piggins’ first challenge was to homologate (certify) an engine that came in under the Trans-Am displacement limit of 5.0L (305 cubic inches). Chevrolet offered 283-ci and 327-ci engines, but nothing in between. The 283 wasn’t stout enough and the 327 was too large, but Piggins deduced that mating the four-inch bore of the 327 with the three-inch stroke of the 283 provided a displacement of 302.4 cubic inches. This was a tried and true combination that 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. That of course is what a race engine has to do—run for sustained durations at high rpm.
The small-journal, cast-iron block for the 302 was also shared with the 327 and the 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 reliefs. The iron heads featured big 2.02-inch intake and 1.60-inch exhaust valves with wide passages and big ports to produce 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, dual-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 headers optional. A single point Delco-Remy ignition was standard with a transistorized ignition optional. Chevrolet blatantly underrated the 302’s horsepower at 290 and torque an equally silly 290 lb-ft. In reality, the production engines generated over 375 hp, with power coming on strong from 3,500 to 6,500 rpm and still pulling at 7,000 rpm.
Piggins’ concept of using off-the-shelf components to build both a spirited performance street engine and a wicked race engine had another advantage—he could come to market with a production engine at significant cost savings. That would make it easier to sell the program to Chevrolet management. The rest of the package consisted of a heavy-duty radiator, quick steering, 15x6 wheels on 7.35x15 nylon red stripe tires, a four-speed Muncie M21 close-ratio manual transmission, special springs and shocks, a 3.73:1 rear axle and special wide stripes on the hood and rear deck lid.
Mandatory options included power brakes with front discs and metallic rear drums. Chevrolet Product Planning assigned it the next available RPO package number on the list—Z/28. The RPO number became the model name for Chevrolet’s Trans-Am contender.