Development Dually: A ZZ632/1000-powered 1989 Silverado Concept

Not long ago, Chevrolet Performance’s 1989 Silverado dually was headed for the scrap pile at the GM Milford Proving Ground in Michigan. However, an 11th-hour save gave the truck a second life – and now it is a showcase for the Bowtie’s impressive ZZ632/1000 crate engine.*

The truck^† recently made the rounds on the 2024 HOT ROD Power Tour as an example of how the impressive Big-Block power plant can bring new life to an old, well-worn vehicle.

Throughout Power Tour, Jeff Walker, General Motors Engineering Group Manager – Performance Software and Calibration, was responsible for driving the truck to each of the five stops in five days. The engine performed flawlessly along the entire grueling route.

Walker told the Silverado’s story during this year’s first Power Tour stop at Beech Bend Park in Bowling Green, Kentucky. 
 
“For most of its life it had lived out in California or the Southwest; we believe it was all within GM's hands,” said Walker, who has worked at General Motors for 14 years. “It was out at the scrap lot getting scrapped out because nobody needed it, but as the 632 was coming online, it was the perfect fit. [The truck] had most of the space under the hood and a big enough engine compartment. Off we went. 
 
“We wanted to bring it here so that participants can see what’s out there, it’s not just $100,000 builds. This is something you could pick up from a farm. Drop the 632 in and you’ve got a great package to go with it.” 

The ZZ632 was introduced in late 2021, and at 632 cubic inches, is the largest-displacement crate engine* in the Chevrolet Performance family. It’s the most powerful, too, capable of 1,004 horsepower and 876 lb.-ft. of torque on 93-octane pump gas. The engine is built on a cast-iron, tall-deck Sportsman Bowtie block with four-bolt main caps and features forged internals.

While the ZZ632 carries on Chevrolet’s long Big-Block tradition, this engine utilizes modern EFI technology for precise fuel control. It also incorporates a pre-programmed, self-learning ECU, something Walker’s team has taken painstaking steps to create.

“You really can just bolt it in, connect your power and turn the key,” Walker said.  
 
With the Silverado dually having been built to tow, it could handle the power of the massive engine and provide the GM team a unique test bed for the engine.

Walker’s team spent time with the ZZ632-powered truck in GM’s environmental facility to ensure all components were dialed in properly, and also drove the vehicle around the Milford Proving Ground in a variety of conditions to refine cold start, idle, drivability and shift points. Throughout the process, they utilized the vast resources within General Motors to test and prove the engine would be a good choice for the customer in an older vehicle.

The truck also spent multiple weeks in a refrigerated chamber where starts were constantly tweaked to ensure that whenever a customer wanted to move their ZZ632, the vehicle would start up reliably. Among the calibration-development instrumentation additions are eight cylinder pressure transducers and eight wideband 02 sensors. 

The team added a scoop to the hood to allow space for the air cleaner, mated the truck to a 4L85-E transmission built to handle the ZZ632 output and added a Detroit locker to the rear end. They also added new front control arms and bushings, refreshed the brakes, and added a second fuel tank. However, the rest of the truck is almost entirely as it was found in the scrap yard.

“We put some new parts onto it, but we haven't touched the suspension, haven't touched the frame and the interior is ratty just like it was,” Walker said of the test-mule truck.

The red-and-tan two-tone exterior has also faded with age, with the natural patina only adding to the truck’s character.

The result was a head-turning addition to the Chevrolet Performance fleet during this year’s Power Tour. Hundreds of attendees were drawn to the truck, with a label under the hood defining the Silverado as a “Crate Engine Development Vehicle.” 

Along the way, Walker and his colleagues spent countless hours speaking with event attendees about how GM’s extensive testing and development processes are passed on to the consumer. 
 
“We try to make it so when the customer gets it, it just works,” he said. 
 
The ZZ632/1000-equipped Silverado certainly works. 
 
Be sure to keep watching The BLOCK for more the 2024 edition of HOT ROD Power Tour. 
 
*Because of their effect on a vehicle’s emissions performance, these engines are intended exclusively for use in competition vehicles. These engines are designed and intended for use in vehicles operated exclusively for competition: in racing or organized competition on courses separate from public roads, streets or highways. Installation or use of these engines on a vehicle operated on public roads, streets or highways is likely to violate U.S., Canadian, and state and provincial laws and regulations related to motor vehicle emissions. 
 
†Vehicle shown not available for purchase.