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ZL1 A Chevy Big-Block Legend - ZL1 At A Time

On The Assembly Line With GM's Limited Production, All-Aluminum Ram Jet Big-Block

Barry Kluczyk Dec 1, 2003
Sucp_0312_01_z Crate_ram_jet_zl1 Engine_block 2/22

Just the name "ZL1" conjures thoughts of the ultimate Chevy big-block-a legend in its own time.

As any dedicated Bow-Tie fan knows, the ZL1 engine was a special, all-aluminum version of the Rat motor. That means the block and cylinder heads. In its day, a few were slipped into production vehicles, including 69 '69 COPO Camaros and a pair of super-rare '69 Corvettes.

A couple hundred more of the engines were made available to racers through the early '70s, including John Greenwood, who had considerable success using one of these alloy powerplants in his SCCA national championship-winning Vette.

The ZL1 legend might have remained a tall tale of the Chevy performance mythology, but it was brought into the 21st century when the engine block's original tooling was discovered a few years ago. After a few updates to the initial design, to improve oiling and increase overall strength, GM added an all-new ZL1 assembly to its Performance Parts repertoire.

Sucp_0312_03_z Crate_ram_jet_zl1 Assembly_and_crew 3/22

And, recognizing the success of previous special-edition crate engines, such as the ZZ-430, GM rightfully decided to offer a unique crate engine based on the alloy Rat-the Ram Jet ZL1. The port-injected combination is rated at 510 horses and 493 ft-lb of torque, and includes the necessary computer to manage the electronically controlled engine.

Other changes were made to the engine, too, to update the ZL1 to modern performance expectations, including a roller camshaft (albeit a solid roller). The Ram Jet induction setup is the same offered on other big-block crate engines.

There's one big difference between the ZL1 of old and its contemporary reincarnation, however: displacement. The '69 ZL1 displaced 427 ci, while the ZL1 crate motor is a 454. Why? Because GM says the longer-stroke 454 produces a broader torque curve, resulting in a better driving engine.

Only 200 of the engines were built, each specially numbered with engraved valve covers and throttle body.

The engines were painstakingly put together on a unique, three-station assembly line in suburban Detroit. GM sub-contracted the assembly duties to Performance Assembly Solutions (PAS), which collected the individual components, assembled the engines, and crated them for delivery.

Sucp_0312_04_z Crate_ram_jet_zl1 Engine_crates 4/22

Recently we were fortunate enough to get an exclusive peek at the PAS assembly line, and followed the assembly of several of the Ram Jet ZL1 engines. Interestingly, the engines aren't completely finished when the reach the end of the line.

"With the Ram Jet upper intake, the engines are too difficult to install in a vehicle, so the engines are shipped without the intake manifold installed to save the customer time and effort," says PAS's Chris Zucker. "There are actually two crates with the package; one contains the long-block and many accessories, and the second crate contains the upper intake, the starter and other things."

A start-up kit accompanies each engine, and contains detailed instruction for installing the remaining parts, as well as an oil pump primer. There's also a diagnostic code reader that helps diagnose any problems down the road.

"The timing for each ZL1 is roughed in on the assembly line," says Zucker. "But, of course, the owner really has to fine tune it per the provided instructions."

Creation of the engines really starts at Swartz Machine Company, in Warren, Michigan, where the aluminum block castings are machined. They're delivered to PAS in ZL1-labled crates, hoisted on to engine stands, and then the air and torque wrenches really begin to turn.

"The blocks are measured and inspected before any assembly is started," says Zucker.

In the three stages of the engines' journey down the line, the first stage lays the crank, main caps, cam, timing chain and cover. The second stage completes the short-block, while the third stage finishes the long-block and "dresses" the engine, as well as performs details such as lashing the valves.

Sucp_0312_11_z Crate_ram_jet_zl1 Measuring_tool 8/22

Although the three-stage system is referred to as an assembly line, there are only three or four technicians involved in getting the engines ready for the crates. And while air tools help to quickly cinch certain components, all final fastening is completed with torque wrenches.

"We call it an assembly line, but the engines really are built by hand," says Zucker. "There are very exact standards and tolerances for building these engines, and we follow them to the letter."

Because the engines aren't fully assembled or timed at PAS, they aren't fired up at the end of the line.

"We certainly turn over the engines to ensure the clearance and fit of everything," says Zucker. "However, the manner in which we ship the engines prevents us from starting them up."

Sucp_0312_12_z Crate_ram_jet_zl1 Hydraulic_roller 9/22

From the time the ZL1 block is lifted from its crate to the time the completed engine is ready for placement in its final shipping crate, approximately 8 hours is spent assembling and inspecting it. The steady movement of the line, however, permits five or six engines to be produced in a day.

Once completed, the engines and their ancillary hardware are placed in wood shipping crates for distribution.

"Everybody at PAS is really proud to be involved with the ZL1 project," says Zucker. "There's just so much history with the engine, and everyone is cognizant of that when they're working on these new versions."

And for 200 lucky enthusiasts, their cars will carry on the ZL1 legend-with a modern twist.

Where Do I Get One?Good question. Since only 200 Ram Jet ZL1 engines were built, you'd think they'd have all been snapped up by now, right?Probably.

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Based on the time it takes us to write a story and for you to see it in print, there's a good chance the limited production engines will all have been purchased by the time you read this.

But this is America, after all, and we're certain many enterprising enthusiasts and dealers have held on to their ZL1s in order to make a buck or two. As we finished our story, a quick check on the Web found plenty of ZL1 engines available through sources like Scoggin-Dickey,, and Oregon's Sallee Chevrolet (they had five of the engines in stock).

Be warned, though, the Ram Jet ZL1 isn't cheap...far from it. The lowest price for an engine we saw was $21,500. GMPartsDirect had engine #1 and simply said they were "taking bids" on it. Uh-huh.

If you're bound and determined to put a ZL1 in your Bow-Tie, shop around and compare prices. Start with the Internet and see what's out there. We're sure you'll find several to pick from.

Use the prices of different vendors as leverage to get your best deal. Good luck!



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