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BY Barry Kluczyk Photography by The Author

hevrolet Performance’s all-new ZZ632 crate engine is simply the biggest, baddest, and most powerful big-block ever from Chevrolet. It’s rated at a stunning 1,004 hp and 860 lb-ft of torque—with Pro Stock–inspired spread-port cylinder heads and other modern technologies that enable that incredible performance on 93-octane pump gas.

In fact, the ZZ632 is designed for dual-purpose performance. Electronic fuel injection, advanced ignition technology, and a carefully developed hydraulic roller camshaft profile contribute to a unique balance of great driveability on the boulevard, while the all-new RSX spread-port cylinder heads—named for Chevrolet Performance engineer Ron Sperry, who helped develop Chevrolet racing engines—support amazing high-rpm capability on the dragstrip.

“We challenged ourselves to take big-block street performance to the next level and 1,000 hp on pump gas was it,” Alin Dragoiu, Chevrolet’s design release engineer for the engine, says. “The ZZ632 has dual capabilities, but it was first and foremost designed as a street engine, so we had to balance maximum power with idle quality and other such considerations.”


  • A Sportsman tall-deck cylinder block with huge 4.600-inch bores
  • An all-forged rotating assembly, including a 4340-forged crankshaft with a long 4.750-inch stroke
  • A 12:1 compression ratio
  • Electronic port fuel injection with a throttle body mounted on a high-rise intake manifold
  • A precise 58X crank-trigger ignition system with individual coil-near-plug ignition coils and those huge-flowing RSX cylinder heads
  • A Holley-supplied control system
Yes, a 12:1 compression ratio is high for a pump-gas engine, but that’s where the precision of the crank-trigger ignition and electronically controlled fuel injection pay big dividends.

“We couldn’t get away with such high compression without them,” Dragoiu says. “They enable the balance we’re able to strike between low-speed streetability and the high-rpm performance of a racing engine.”

It’s worth noting here, too, that when it comes to the ZZ632’s assembly, Chevrolet treats it very much like a racing engine. In fact, it’s built by the same technicians as other racing engines, such as the COPO program, the Corvette Racing program, and more, with hand assembly from start to finish by a single builder—a process that doesn’t happen with other production-based crate engines.

“This is a very unique crate engine for Chevrolet Performance, with performance capability unlike anything else in the portfolio,” Dragoiu says. “So, we take extra care to ensure every last detail on the assembly, from file-fitting the rings to checking every last bearing clearance.”

We recently got a glimpse of the hand-assembly process when Chevrolet Performance allowed us to follow the build of the very first production ZZ632. There’s much going on in this distinctive and groundbreaking big-block street engine, so we’re splitting our story into two parts.

This first installment follows the short-block assembly, and our follow-up article will delve into the Pro Stock–derived cylinder heads, fuel and ignition systems, and more—including allaying concerns regarding whether the combined height of the tall-deck block, tall heads, and gorgeous cast-aluminum valve covers will pose a brake booster interference problem in your vehicle.

Spoiler alert: Vacuum is not this engine’s strong suit, so you’ll probably want to investigate hydroboost systems.

We’ll also discuss the engine’s dyno performance, so you’ll want to stay tuned. For now, follow along as we build up the all-forged short-block.

Chevy Performance 632ci engine on stand
1. The ZZ632 is a big-block crate engine unlike anything previously offered by Chevrolet Performance. It is rated at 1,004 hp and 860 lb-ft of torque on 93-octane gasoline. Such stellar pump-gas performance is due in no small part to electronic fuel injection and a more precise crank-triggered ignition system with individual coils.
Chevy Performance 632ci cylinder head
2. With a 7,000-rpm capability and 632 ci, the engine needs airflow like a beach needs sand. It’s processed through new, parallel-port RSX cylinder heads. They’re the heart of the ZZ632’s capability and we’ll explore them further in part 2 of the story.
Wilson Manifolds throttle body on 632ci engine
3. Air enters through a Wilson Manifolds Dominator-style throttle body as part of the engine’s electronic fuel injection system. Again, more on the aspirational aspects of the ZZ632 in the next installment.
Bare 632 engine block
4. The engine’s foundation is a CNC-machined Bowtie Sportsman tall-deck block with a one-piece rear main seal design. Compared to the conventional big-block casting, the Bowtie Sportsman block has a revised water jacket design to accommodate up to a 4.600-inch bore.
Closeup of bored cylinder ports
5. A 4.600-inch bore is exactly what the ZZ632 has, while its 10.200-inch deck height is 0.600-inch taller than the conventional big-block, providing more room for longer connecting rods and a more optimal rod/stroke ratio. Look closely and you’ll see the edges of the block have been deburred as part of the hand-assembly process.
Closeup of valvetrain valley
6. The valley is machined for a roller-type valvetrain, which the engine employs to enhance its streetability.
Bare bottom half of 632 engine block
7. The bottom of the block is machined for splayed main caps. They’re used with Clevite Tri-Metal bearings. Only the top shell of the bearings are grooved. The bottom shell bears the majority of the load, so it is not grooved in order to maximize surface area. Also of note is the fuel pump mounting pad. It will be blocked off because the EFI system requires the pressure of an electric pump.
Notched cylinder bottoms for clearance
8. Even with the tall-deck block, the engine’s long stroke requires the bottoms of the cylinders to be notched for clearance.
Notched oil pan rail
9. The same goes for the oil pan rail. It’s machined for rod clearance.
Disassembled pistons with 6.66" connecting rods
10. There’s only so much room, even within a tall-deck block, and the forged Compstar H-beam connecting rods measure 6.660 inches in length. That’s more than a 1/2-inch longer than the rods of a production 427 or 454, but with the 4.750-inch stroke the rod/stroke ratio comes in a little less than ideal, at 1.40:1. But like we said, there’s only so much room in the block, even with the notched cylinders and pan rail.
Underside of Mahle piston heads
11. The forged aluminum pistons come from Mahle and are used with full-floating pins. Additionally, the ring pack is a more modern design, with 1mm-wide top and middle rings, compared to earlier big-block designs, which helps reduce friction. The oil scraper is a 3mm ring. Additionally, coatings on the piston skirts also help reduce friction, helping offset side loading on the cylinder walls.
Top of dished piston heads
12. A couple things to note here with the piston design: For one thing, it’s dished, compared to the typical domed design of big-block engines because the combustion chambers of the RSX cylinder heads are comparatively small and the dish helps keep down the compression ratio to “only” 12.0:1. Also: the piston is comparatively short, with the pin intruding on the bottom ring land. This was done to push the rod as far up on the piston as possible in order to stretch the rod length as far as possible.
Roller being inserted into camshaft
13. Along with the all-new heads, an all-new camshaft profile was developed to help deliver the engine’s balance of low-speed tractability and high-rpm max performance. It’s a billet steel hydraulic roller supplied by Comp Cams and its specs include a whopping 0.780/0.782-inch lift (intake and exhaust), 270/285 degrees duration (intake and exhaust), and a midrange 113-degree lobe separation angle. It gives the engine a good idle quality—with an unmistakable lope—while helping deliver airflow all the way to 7,000 rpm. Not much in the way of vacuum production, however.
4340 forging Callies crankshaft
14. Next comes the crankshaft. It’s a 4340 forging from Callies, giving the engine its enormous 4.750-inch stroke. A production 454 stroke is only 4.000 inches. A 454 is also externally balanced, while the ZZ632 is internally balanced. The crank is also used with a one-piece rear main seal.
Closeup of crankshaft
15. The crank is located with splayed, billet steel main caps, with the outer fasteners splayed at a 16-degree angle. The caps are secured with ARP fasteners. Also: Note the chamfered oil holes on the crankshaft journals, which reduces shearing of the oil flow as it exits the oil passages. That enhances the oil flow, helping cool and support the crank journal and connecting rod bearings.
Melling M77 oil pump
16. The proven Melling M77 high-volume oil pump is used to push Mobil 10W-50 through the engine.
Pistons being inserted into engine
17. With the crankshaft in place, the rods and pistons were slipped in next—each one by hand, like a custom racing engine. That’s the way the entire engine is assembled, and all by a single builder from start to finish.
58X reluctor wheel on crankshaft snout
18. In addition to a double-roller timing chain, a 58X reluctor wheel is slipped over the crankshaft snout to support the crank-trigger ignition system. A keyway on the crankshaft ensures it won’t slip out of place.
8" ATI Super Damper
19. The assembly includes an 8-inch-diameter ATI Super Damper, which is unique to the ZZ632 because the shell is trimmed 3 mm in the back to accommodate the reluctor wheel.
Crankshaft position sensor
20. The unique timing cover also includes mounting provisions for the ignition system’s camshaft and crankshaft position sensors. The crankshaft sensor is shown. Most of the sensors used on the engine are off-the-shelf parts from the LS3 and other GM production engines.
Fully assembled Chevy Performance 632ci engine
21. In Part 2 of our look at the ZZ632’s assembly, we’ll follow the installation of the top end, including the heads, fuel system, and ignition system to finish off the engine. You’ll definitely want to check out the results in the next issue.
Chevrolet Performance
Gandrud Chevrolet