The History of the ZL1

  • ZL1 engines were not painted red, while cast iron big blocks were. - 0
  • ZL1 engines included power saving clutch fans and forced air induction. - 1
  • In 1971, Fred Gibb’s ZL1 Camaro held the AHRA national record in Pro Stock at 9.63 seconds and 143 mph. - 2
  • Fuel flowed through dual 4500 dominator carburetors. - 3
  • The compression ratio was 12.7:1. - 4
  • A Dana 60 axle supplied power to the ground. - 5
  • This is 1969 Camaro ZL1 #40. - 6
  • The ZL1 block casting number for 1969. - 7
  • 1969 Camaro ZL1 blocks were all aluminum with a casting number of 3946052. - 8
  • All ZL1 cars came with aluminum heads. Intake valves were 2.19" and exhaust valves were 1.88". - 9
  • The ZL1 crankshaft is made from 5140 steel tuftrided and cross drilled. The last four digits of the casting number were 7115. - 10
  • A Holley 4296 850 cfm dual feed double pumper was used on ZL1 cars. - 11
  • All ZL1 blocks were produced by Winters Foundry, noted for its trademarked snowflake symbol cast into the block. - 12
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by Joe Babiasz  More from Author

Blazing Fast, Powerful, and Impossible to Sell

Perhaps no other engine earned more respect during the factory muscle car era than Chevrolet’s ZL1. Not only did it offer pavement-melting power, but it also represented a time when General Motors, or more correctly, a small group of speed freaks within the corporation, could pull off a stunt like producing the ZL1 without the blessing of GM’s bureaucrats. The ZL1 program, while brief in its existence, brought Chevrolet to the forefront of factory performance.

The all-aluminum 427ci big block wasn’t specifically designed to be installed under the hood of 1969 Camaros and Corvettes. It actually began several years earlier when Chevrolet, disappointed with their results in the 1966 Can-Am races, needed to increase the horsepower for their race cars. Chevrolet was using their small block in the cars, but quite frankly lacked enough power to win races. The 427 cast iron big block engine was available, but the added weight in the Can-Am cars would be detrimental to handling. Engineering began development of an all-aluminum 427 engine that produced approximately 600 horsepower. The experimental engine debuted in a 1967 Chaparral 2F. Shortly thereafter, it set a record for the fastest lap on the course and became one of the most successful race engines of all time.

As with many experimental powertrains, it eventually find its way into a production vehicle. Enter the 1969 Camaro. Some car nuts at Chevrolet couldn’t think of a better vehicle to drop the ZL1 in. Unfortunately, there was a corporate edict that a Camaro could not have an engine larger than 400 cubic inches. To those in the know, there was only one way to circumvent the policy. It was known as COPO, or Central Office Production Order. COPO was GM’s little-used method of ordering “fleet” cars and was typically used for taxicabs, special paint and special wheelbase trucks. Fortunately for hot rodders, it could also be used to bypass the cubic-inch issue with the Camaro. If someone wanted a ZL1 installed at the factory, they simply wrote COPO 9560 on the order sheet. Adding an AA or BA after the COPO number gave them either a four-speed manual or an automatic transmission.

Before the ZL1 went into production vehicles, it required several changes from the race-ready Can-Am engines. The dry sump system was replaced with a traditional wet sump system and the block was prepped for a mechanical fuel pump. Production cams were modified to withstand street driving. A total of 90 ZL1 engines were produced for factory production. Of these, 69 went into Camaros, two went into Corvettes, two went into 9567 prototypes and the remaining 17 sold as crate engines.

The trouble with ordering a ZL1 was the need to order the necessary quantities. Chevrolet was not going to build just one or two for private customers, as it would be too much trouble. Since the requirement to race in a “stock” classification required at least 50 cars to be produced, Chevrolet made it necessary for a dealer to order at least 50 vehicles before the order would be accepted. Thankfully, Fred Gibb, a successful Chevrolet dealer and drag racer in La Harpe, Illinois, was ready to make such an order. He was well known within Chevrolet and a personal friend of Chevrolet’s General Manager and Vice President Pete Estes. With Pete’s assistance, Fred ordered 50 ZL1 Camaros after learning that the price would be approximately $5,200 – big dollars at the time. Still, he felt he could move them with the help of other dealers to racers nationwide. Fred was anxious for a car to be delivered early enough for Dick Harrell to race it at the AHRA meet in early 1969. Gibb was advised that the cars wouldn’t be delivered in time for the meet. After pleading with Chevrolet, two ZL1 cars were delivered on December 31, 1968. Pete Estes personally made sure the car would be produced for Gibb. The broadcast sheet of these two cars indicated “Estes Request Red-Hot” on them.

It was 22 below zero on the day the cars were delivered, and as the carburetors lacked a choke, neither car would start. Gibb eventually got them into the service bay, and they finally fired up. He would later find out that the starting issues would become the least of his problems. Of the original two, one of the cars was sold to a private party, and the other was set aside for Harrell. In three short weeks, Harrell’s car was prepped and ready for racing at Phoenix. Unfortunately, the car failed tech inspection due to the carburetor not being listed as correct for that particular engine. After a few phone calls to the right people, an engineer flew to Phoenix with the correct carburetor. While the car did well for its first outing, it did not win its class.

Gibb was not without his share of problems. After contracting to purchase 50 cars, he received the invoices for the first two Camaros. The original $5,200 price was actually over $7,300, even though they were ordered with few options. Chevrolet division, without advising Gibb, had changed the rules, and all production costs were now the burden of the buyer. In this case it was Gibb. The actual price of the ZL1 option, called the “High Performance Unit” option, was $4,160.15, which was more than the $2,726 base price of the car. Gibb, who would soon have to write a check for over $363,000 to cover the cost of his 50-car order was overwhelmed. He contacted Chevrolet to plead his case. In an unprecedented move, Chevrolet agreed to take back approximately 30 of the cars, and they were sent back to the Lordstown, Ohio assembly plant.  

Fred Gibb ordered his cars without any comfort features. After all, these were to be drag cars that represented the fastest Chevrolet offered. Unfortunately, this limited sales to the general public. Soon after Gibb placed his order, several other dealers learned of the 9560 option and ordered their own, increasing production of the 1969 Camaro with a ZL1 option to 69 units. The difference between the Gibb cars and other dealer cars was that the other dealers ordered them with several comfort features, including two Rally Sport cars, to improve their opportunity of selling them retail. It was still a very hard sell with the high price, in some cases reaching over $8,000. The other dealers soon found out the car was almost impossible to sell.

All ZL1 Camaros started out as an RPO L78 396ci 375hp Camaro. When COPO 9560 was ordered, the L78 engine was replaced with the ZL1 engine. Also included was a heavy-duty 4.10 posi-traction rear axle, heavy-duty radiator, cowl induction hood, special springs and transistorized ignition. Customers ordered either the automatic or four-speed transmission. As with any solid lifter Chevrolet, air conditioning was not available. Interestingly, the first 50 ZL1 cars were incorrectly produced with a 780 cfm Holley carb. The cars were later retrofitted with the correct, larger Holley carburetor. While the 9560 Camaro produced high horsepower, small tires and restrictive exhausts showed stock ZL1 cars crossing the quarter-mile in just over 13 seconds at about 110 mph. Headers and super-tuning lowered that time to the mid 11s.

So what made the ZL1 engine so special? High on the list of advantages was its light weight. Using aluminum brought the big block’s weigh very close to the weight of a small block, around 500 pounds. Another advantage was that it started out as a race engine, and much of that technology was kept for the production powerplant. The icing on the cake was the breathing ability of the big block. Specifications were nearly identical to the production version of Chevrolet’s L88 but included a tweaked cam and a specially-tuned aluminum intake manifold. Open chamber heads moved the air/fuel mixture like gale force winds. All ZL1 blocks were produced by Winters Foundry, noted for its trademarked snowflake symbol cast into the block. While a production line horsepower (with all accessories and stock exhaust system) peaked at only 376, when accessories were removed and headers installed, horsepower jumped to 524. That’s not bad for a production car engine forty years ago.

Chevrolet soon recognized that the ZL1 would be difficult, if not impossible, to sell. In response to the cold shoulder customers gave, Vince Piggins and his GM design staff built two COPO 9567 prototypes. It wasn’t an attempt to build a cheaper ZL1 but to build a more streetable car. The Camaro was to come with a Muncie M21 four-speed transmission and an 11:1 compression ratio. Both prototypes were Tuxedo Black in color with gold stripes. The price was pegged at an astronomical $8581.60. Needless to say, the COPO 9567 Camaro never made it into production.

In the end, the Camaro ZL1 saga was a difficult time for Chevrolet and their dealers. Fred Gibb was able to send a portion of his cars back to Chevrolet. Other cars went to other dealers in an attempt to sell them. Only 13 cars were sold directly through Fred’s dealership. About 20 cars were prepped for NHRA Super Stock class, and others were sold to private owners. Many dealers who ordered a ZL1 Camaro wound up removing the ZL1 engine and replacing it with a cast iron 396 or 427 in an effort to sell the car. Several other cars were stolen and never recovered. Interestingly, it took until 1972 for Fred Gibb to sell the last 1969 ZL1 Camaro sitting on his lot. It sold with a $1,000 rebate from Chevrolet. Unfortunately for Gibb, it was repossessed and returned to his dealership in 1973. It is safe to assume that he hated to see it come back.

Luckily for automotive enthusiasts, Chevrolet was required to retain a list of all ZL1 Camaros produced, and today this is very important for verification. Without proper documentation, these cars would be lost in the shuffle of the “was it an original big-block car” wars. Several cars are still unaccounted for, but enthusiasts around the world are still searching for this rare factory racecar. Today, it is known that 50 cars still exist. Many have been accounted for, and a few are back on the racing circuit, showing today’s generation what 1960s drag racing was all about.

Many said the potential was there for a fire-breathing factory racecar to dominate the drag race scene. But the high cost, low production run and durability issues of the early cars came into play. Some think that an L88 Camaro would have been a better idea. By the end of 1969, corporate interest in the ZL1 program dwindled. The people who brought it to production moved on to other jobs. Pete Estes, the driving force behind the ZL1, left Chevrolet to become GM Group Vice President. John DeLorean replaced him and concentrated on Pontiac’s role in factory performance. Budgets were tight, and the ZL1 program was dropped like a hot potato.

Eventually, the ZL1 Camaro made its name known in the drag race circuit. Racers like Malcom Durham, Dick Harrell and Ken Barnet took an edgy factory racer and recorded quarter-mile times in the low 10s, with speeds of over 132 mph. No other factory racecar would accomplish so much. Today, any documented ZL1 Camaro commands top dollar at collector car auctions. The Dick Harrell Camaro recently sold at the 2009 Barrett Jackson Auction for $319,000. It is expected these rare racecars will continue to increase in value.

On a related note, the ZL1 Camaro was not the rarest ZL1 car for GM – that was the 1969 Corvette ZL1. Unlike the COPO 9560 Camaro, the Corvette ZL1 was considered a factory option. Reports vary in the total of ZL1 Corvettes produced, but the unverified production numbers are two, although it’s possible that up to seven Corvettes were produced with this engine.


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