Every Camaro lover knows the story of the phenomenal 1969 ZL1. Born out of the success of Jim Hall's Chaparral/Chevrolet aluminum big-blocks in the Can Am series, the all-aluminum 1969 ZL1 was based on the legendary Corvette iron block/iron heads L88, but updated with goodies like open chamber heads that moved cubic tons of volume and made enormous horsepower and torque.
It was the dominance of the Cam Am engine that inspired Fred Gibb Chevrolet to suggest to Chevrolet that they develop a package for the Camaro that would accommodate the 427 ZL1 for drag racing. Chevrolet had long been out of "officially" supporting drag racing, leaving only stalwarts like Dick "Mr. Chevrolet" Harrell and Bill "Grumpy" Jenkins to carry the Bow Tie banner down the professional quarter-mile. Gibb and Harrell had an eye toward the upcoming Pro Stock class that would begin with the 1970 NHRA season, and felt a ZL1-equipped Camaro could win big over the Hemi, especially since the 500-pound ZL1 would enjoy a 150-pound advantage over the Elephant engine.
Gibb was no stranger to the COPO program. COPO stood for Central Office Production Order and was used to produce vehicles in limited quantities that were deviations from regular production. The only requirement was that COPOs had to use production parts and be approved by Chevrolet Engineering. COPOs could be used to order anything from a fleet of taxi cabs or school buses to the minimum of special cars to qualify for drag racing.
Gibbs had used the COPO process before to order 50 specially equipped 1968 SS Novas with the 396/375 L78 engine with M40 Turbo Hydra Matics to qualify for NHRA's stock automatic class. Interestingly, this was the first time Chevrolet had ever placed an automatic transmission behind a solid lifter engine. Racers snapped up the package, either from Gibb or Dick Harrell, who was contracted to modify some of the cars through his shop in Kansas City, Missouri. The success of this program led Gibb to decide to do the same with a 427-equipped Camaro. To ensure that the combination would be legal for the 1969 NHRA season, Chevrolet guaranteed that Gibb would receive the first cars before December 31, 1968.
Working with Chevrolet Engineering's Vince Piggins, Gibbs ordered 50 1969 Camaros through the COPO program in the summer of 1968. They started with the L78 Camaro SS with 14x7 wheels, cast-iron exhaust manifolds and F41 heavy-duty suspension. The option was tagged 9560 with the ZL1 all-aluminum engine and a choice of either the M40 Turbo Hydra Matic, M20 wide ratio four-speed, M21 close ratio or heavy service M22 "Rockcrusher" close ratio four-speed (Gibb later deleted the M22, feeling it wasn't worth the cost). A special 15-pound nodular flywheel was used with stick models. Only one rear-axle ratio was specified, a 4.10:1 differential with heat-treated ring and pinion and Posi-traction limited slip. The steel ZL-2 cold air induction hood was included, along with heavy duty springs with five leaf rears, heavy duty radiator, transistorized ignition, power front disc brakes and F70x14 white lettered tires.
All 50 cars received a black vinyl interior, came without radio and were offered in only five colors: Cortez Silver, Fathom Green, Dusk Blue, LeMans Blue and Hugger Orange. Ten cars were built in each color and those ten were split between four equipped with M40s and six with M21 transmissions. The exterior trim was limited to blue Bow Tie emblems on the grille and rear panel and Camaro badges on the header panel, fenders and deck lid. The grilles were Argent Silver. And while iron big-blocks were always painted orange, the ZL1 was left in its all-aluminum glory.
Development of the ZL1 engine moved slowly. The aluminum block required extensive work for street/drag racing use. Cast-iron sleeves were used in the aluminum block, retained with a 1/16-inch groove at the top of the block. The main bearing bulkheads were beefed, and many of the bolt and stud threads throughout the engine were lengthened for greater strength. The forged steel rods were thicker in the caps and the shank base, with bigger 7/16-inch rod bolts. Along with the open chamber design, the heads received bigger exhaust ports than the L88, were round instead of square and boasted bigger 1.88-inch valves. That resulted in exhaust valve lift being increased to .600 and the duration shortened to 359 degrees. The ZL1 was the first Chevrolet production use of the 850-cfm double-pumper Holley carburetor on an open plenum high-rise intake manifold. Chevrolet rated the ZL1 at 430 hp @ 5200 rpm and 450 lb-ft @ 4400 rpm. However, dyno tests of factory ZL1s revealed their output was more in the 550hp range.