BadAssGN

In the early days of racing, select racers enjoyed, in varying degrees, a mutually beneficial relationship with Chevrolet. These racers include Smokey Yunick, Roger Penske, Jim Hall, and Fred Gibb, to name a few. Fred Gibb was a veteran AHRA drag racer and owner of a Chevrolet dealership in La Harpe, Illinois. Due to his direct involvement in drag racing, Fred was no stranger to key people at Chevrolet, including the famous "Product Performance" department. But his closest ally was no less than Chevrolet General Manager (and GM Vice-President) Pete Estes, who could be considered the godfather (with Vince Piggins as father) of the Z/28.
The Camaro was Pete's baby and when it did not perform well in the 1967 Trans-American Series the resources of Chevrolet's massive engineering department were tapped. Photographs exist of the Penske-Donohue Trans-Am Camaro undergoing testing at the GM proving grounds. Soon "Heavy Duty" (read "racing") driveline, suspension, and braking components appeared along with virtually unstreetable engine parts. Camaro went on to win the Trans Am series in 1968 and 1969.

In 1969, Pete's baby was under attack again, but on a different front. Drag racing sanctioning bodies had a simple rule: if at least fifty units of a particular engine/platform combination had been produced, such combination would be considered legal for stock-class racing. Ford was building Mustangs with 428 Cobra Jet engines, Chrysler had commissioned an outside firm to build Hemi Darts and Barracudas, and even lowly AMC was having 401 engines placed into AMXs. Fred Gibb thought a Camaro with the new, aluminum block 427 engine slated for the Corvette (RPO ZL1) would be perfect. But Camaro could not participate, for GM had a corporate policy forbidding the production installation of an engine larger than 400 cubic inches in any non-Corvette passenger vehicle smaller than "full-size". A proposal to management for a production 427 Camaro would take significant time for approval, and even if accepted, would be politically unpopular within the higher levels of GM.

Time was wasting and Fred Gibb wanted to race the car at the AHRA opener in Phoenix, January, 1969. There was an easy way around the corporate bureaucracy: a special fleet order procedure (known internally as the Central Office Production Order) normally used for special paint or equipment on commercial vehicles. (In fact, Fred Gibb had used this trick in 1968 to have fifty COPO L78 Novas built for drag racing with special automatic transmissions.) Fred and Pete decided on equipment that would become part of their new 1969 Camaro package: the aluminum ZL-1 engine, the new cold-air hood, heavy-duty cooling, transistor ignition, and a special rear axle. Additionally, the cars would require mandatory options of F70x14 RWL tires, power front disc brakes, and either a new Turbo 400 automatic or any of three Muncie 4-speed transmissions. Thus Central Office Production Order (COPO) 9560 was born. The cars were emissions-certified, carried both the 12/12 and 5/50 warranties, and were street-legal. Gibb received verbal assurance that the option price would be around $2000. During October 1968, fifty 1969 ZL-1 Camaros were ordered for delivery to Fred Gibb Chevrolet: four automatics and six M21 4-speeds each in the five colors of Dusk blue, Fathom green, Cortez silver, Le Mans blue, and Hugger orange. No other options were specified, not even radios.

The AMA specifications filed for COPO 9560 listed horsepower at 430 and shipping weight at around 3300 pounds. Fred and Pete probably did not realize they had just created the most powerful passenger car Detroit ever built.



The ZL1 Engine

The origins of the ZL-1 engine trace back to the SCCA's Can-Am Challenge Cup series of the mid-'60s. Chevrolet was providing engineering assistance and parts to Jim Hall's Chaparral racing team that was using aluminum 327 engines at the time. The engines had reached the end of their development and more power was needed for Chaparral to remain competitive. Since the big-block was well along in power development and reliability due to Chevrolets' involvement with the Smokey Yunick / Curtis Turner NASCAR effort, it offered the path of least resistance. But the Chaparral did not want the added weight of a cast-iron engine, so it would have to be developed in aluminum.
The transition to aluminum was not an easy one. Most of the 1967 season was spent making the new engine survive. By the end of the season the bugs had been worked out and the aluminum 427 engine was powerful and reliable. At that time Jim Hall was the exclusive customer for the engine. For the 1968 Can-Am season other racers were able to acquire it, most notably McLaren Racing with its famous orange cars. It was extremely successful and Chevrolet began to think the engine could have a market as an option in the Corvette. It was transferred to the production engine group and some efforts were made to publicize it. Hot Rod magazine did a feature article on it with a cover photo for the December 1968 issue.

In production form, the engine differed from Can-Am configuration. The dry-sump oil passage was eliminated and provision for a mechanical fuel pump added. Production tooling was developed for the block (casting #3946052), cylinder heads (#3946074), and intake manifold (#3933198). A new aluminum water pump was to be included (and at least one and perhaps two Camaros were built with it), but last minute testing raised reliability questions.

Chevrolet continued to develop the Can-Am version of the aluminum big block for racing, progressing to a liner-less 390-alloy block buildable in displacements of 430, 441, 494 and 510 cubic inches. These did not have provision for a mechanical fuel pump. They were never used in production and few were produced.



Production ZL-1 engines were intended for Corvette installation. An engineering document was issued listing the parts to be changed for installation in a Camaro. The assembled engines were not painted as normal cast iron engines but certain steel components were painted. The engine assembly manual shows that "black engine enam" was to be used to paint the "oil pan, air inj brkt, distr clamp, frt cover, clutch fork (exposed part), torsional damper, lifting hook, exh manif, clutch hsg cover".
Some new component parts were necessary to accommodate the ZL-1 engine. New "HQ" code front springs were developed for the weight change. Engineering drawings were produced detailing the assembly of the K66 transistorized ignition system in a 1969 Camaro, including the design of an ignition amplifier mounting plate and a small harness to adapt the K66 ignition to the Camaro engine wiring.

ZL-1 cylinder heads do not have an exhaust heat crossover passage so a spacer was used in place of the heat-riser valve on the RH exhaust manifold. Also because of this, the carburetor had no choke. The AMA specs specified an 850 cfm Holley model #4296 carburetor. But due to supply problems most cars were built with 780 cfm Holley model #4346 carburetors, though many were later retrofitted with the #4296. A rebuildable hi-performance AC fuel pump was used. The ZL-1 engine was built with a crankcase windage tray that interfered with the baffle in the production 4-quart oil pan. For this installation the standard pans were modified by removing the baffle.

Fred Gibbs' drag racing experience had found the limits of the standard production rear axle. A stronger positraction unit with larger pinion and axle gears was developed. This new unit was used with a heat-treated 4.10:1 ring and pinion. It was coded "BE", instead of the standard 4.10 Camaro axle code of "BV".

The remainder of the car was built using standard assembly procedures and components as employed on a Camaro SS with the L78 engine, with some other exceptions. A document titled "Exception control letter sheet" was used to outline parts that were to be deleted and / or substituted from the SS L78 package. One example is the starter: an L78 used an 11" clutch, the ZL-1 used the 10.34", and so starter 1108418 was replaced with 1108351 on the 4-speed and 1108400 on the automatics. This system also explains why COPO's built as rally sports do not have the rally sport fender emblems. The "Camaro SS" badging was initially specified and the document "deducted" the SS, leaving only the "Camaro" emblem. There was no external indication of the engine. Assembly line workers wrote "427" in crayon on the inside of the fender extensions so the fenders would not be pierced for emblems as all other 8 cylinder Camaros were. All ZL-1 cars were equipped with AIR pumps and Gibbs' cars were produced with standard N10 dual exhaust.

Plain Jane Camaro with all that Hp....

R/T kota

Got anything on the ZL1 vette?

BadAssGN

I think so, I'll look in the morning, I'm on my Laptop right now