Anniversary 427 Big-Block
New for 2008, GM Performance Parts re-releases the vaunted ZL1 crate engine. Built off of the original (and restored) tooling, it's as close to the real thing that you can get without going back in time to 1969. Adding to the collectible status is a limited production run (only 427 will be built) and matching serial-numbered valve covers, engine bay tag, emblems, and certificate of authenticity (not shown). With only 427 of these super-rare all-aluminum 427 big-block crate engines available, it will be one of the hottest GM crate engines built in 2008. Final horsepower rating will come in around 480 hp-on pump gas. MSRP will be around $20K, but typical street price will be in the $16K range.

The "W" series V-8 engine first debuted in the 1958 line of Chevrolet trucks and passenger cars, and it would go on to help define a generation of classic engine options for car enthusiasts. It had the traditional overhead valve design with offset valves, and came in 348, 409, and 427ci versions up to 1965, when the Mark IV series of big-block GM engines were released. The Mark IV engines had different valve placement and combustion chamber shape-advancements made through GM's testing for NASCAR competition. The biggest improvement was a traditional wedge-shaped chamber that sat in the head (now on a 90-degree deck), not in the block as the "W" engines had used. Spark plug location was also changed, but the cylinder bore spacing, main web layout, and several other features remained true to the first member of this engine family. In the end, the Mark IV engines were more efficient, could operate at a higher rpm, and offered more power potential than its predecessor. GM called the new engine the "Turbo Jet," and the dawn of the big-block rat was upon us.

While GM cranked out all sorts of production cars stuffed with 396-, 427-, and 454-inch fire-breathing street slayers, hot rod builders gravitated to the big-block engines as well. Other than pulling a used engine from the scrap yard, the first place you could get a GM engine (and the originators of the crate engine concept) was a small division of GM that started selling high-performance parts and engines through its dealer network in 1967. That team of performance enthusiasts grew up to become what is today known as GM Performance Parts, and one of its very first crate engines was the L88 427 big-block of the late '60s. Fifty years have passed since the first GM big-block was born and GM Performance Parts is looking to celebrate that 50-year anniversary in a very big way.

To celebrate this auspicious occasion, GM Performance Parts has looked at the history books and zoomed in on the legendary ZL1. "ZL1" is perhaps the most coveted GM RPO code in the history of Chevrolet. It represents the option code for one of the rarest of rare big-block rats: an all-aluminum 427-inch monster that only a precious few production cars ever came with. Only two Corvettes and '69 Camaros were ever delivered with the ZL1 engine option code, but that was enough to make history for this vaunted engine.

What makes the ZL1 so special? This engine, developed through years of Can-Am racing, represented the culmination of years of developmental work by GM. By 1967, Chevrolet had rolled out the L88, which measured 427 ci. It was a high-compression, solid-roller filled, aluminum-headed race motor that found its way onto the streets of America (and into PHR's Project X in 1969). The L88 was available as an engine option in the Corvette and COPO option for Camaro, and as a crate engine until 1969, at which time the ZL1 made its debut. What separated the ZL1 from the other 427 engines was the use of an aluminum block, which knocked a whopping 100 pounds off the total mass of the engine. For road race cars, this allowed for an extremely well-balanced suspension setup. For drag racing, more weight (a higher percentage) was placed over the rear axles, increasing weight transfer and ultimately allowing for better traction.

The ZL1 option was expensive at $4,718, probably accounting for the low number of cars so equipped. Still, you got a lot of race engine for the money. The aluminum ZL1 block was the top draw, but there was so much more. The L88 large-port aluminum heads were revised to offer an open combustion-chamber design that yielded a 12.25:1 final compression ratio. [The July 1969 issue of Popular Hot Rodding stated the original ZL1 compression ratio at 12:1.-ed.] The intake was aluminum and wore an 850-cfm Holley four-barrel. With a high-lift mechanical roller, the ZL1 (as well as the L88) was rated at 430 hp at 5,200 rpm and 450 lb-ft of torque at 4,400 rpm. Experts place the actual power at 500 hp at 6,400 rpm (the true peak of such a big cam). And, with headers and open exhaust, the mighty ZL1 could belt out between 550 and 575 hp. But, it was a race engine that demanded high-octane race fuel and judicious tuning. It started hard, idled rough, and ran like a scalded dog. [ZL1-equipped Camaros were able to run 10.20s with slicks, long-tube headers, a high-rise Weiand manifold, dual Holley 660-cfm carbs, and a turbo-clutch transmission, a test PHR performed in the July '69 issue with help from Dick Harrell.-ed.]

As we pointed out earlier, the high-performance crate engines offered up by certain GM dealers helped launch what is today GM Performance Parts. In 1969, you could buy a ZL1 crate engine for a couple thousand dollars, and GMPP still offers the ZL1 block for those who want to take advantage of its lightweight design. Looking back to where they started, the good folks at GMPP decided to give the ZL1 another run. So, for the first time since the early '70s, GMPP will once again make available an aluminum-block 427-inch big-block that holds true to the legend of the ZL1. Called the Anniversary 427 Big-Block crate engine, it is based on the ZL1 block, features a forged rotating assembly, oval-port big-block heads, a matching oval-port intake, and all the associated hardware you need to have a brand-new ZL1 right out of the box. A hydraulic roller cam, a smaller 770-cfm carb and a 10.1:1 compression ratio are the only divergence from the original, but those changes allow for a pump-gas crate engine that will still crank out a conservatively rated 430 hp-just like the original.

This is a true collector's engine, with only 427 of the units being produced. The engines will also come with a leather-bound owner's kit that includes a certificate of authenticity, special badging for the lucky vehicle that gets the engine, and further documentation on the pedigree of this engine. In this PHR feature, we've got an advance look at what parts will be going into this history-making big-block crate engine from GM.