If you're wondering is a 5.7 Hemi a big block, the short answer is no, but there's a lot more to the story than just a simple "yes" or "no" when you're looking under the hood of a modern Ram or Charger. For decades, the terms "small block" and "big block" have been tossed around car shows and garages like they're the only two categories that matter. Usually, it's a way of bragging—if you've got a big block, you've got the heavy hitter. But when it comes to the 5.7-liter Hemi that Chrysler (now Stellantis) has been pumping out since 2003, the lines get a little blurry for some folks.
To be technically accurate, the 5.7 Hemi belongs to what Chrysler calls the "Gen III" Hemi family. This engine family was designed to replace the old LA-series small blocks (like the 318 and 360) and the later Magnum engines. From an architectural standpoint, the 5.7 is definitely a small block. It has a relatively compact footprint compared to the monster engines of the 1960s, and its displacement—345 cubic inches—puts it squarely in small block territory.
Why the Confusion Even Exists
It's easy to see why someone would ask is a 5.7 Hemi a big block in the first place. For one, the name "Hemi" carries a massive amount of historical weight. When most people hear that word, their minds immediately jump to the legendary 426 Hemi from the muscle car era. That engine, known as "The Elephant," was a massive, heavy, wide-bodied big block that dominated NASCAR and drag strips. Because the modern 5.7 shares the Hemi name, people naturally assume it shares that "big block" DNA.
Another reason for the confusion is the sheer size of the engine bay in modern trucks and SUVs. When you pop the hood of a Ram 1500, the 5.7 Hemi looks absolutely huge. It's got wide cylinder heads, which is a byproduct of the Hemi-ish valve arrangement, and it fills up the space in a way that an old Chevy 350 just doesn't. Plus, let's be real—the 5.7 Hemi sounds like a big block. It's got that deep, rhythmic rumble that makes you think there's a massive amount of iron moving under the hood.
Small Block Architecture, Big Block Power
Even though it's technically a small block, the 5.7 Hemi doesn't really act like a traditional one. Most small blocks are known for being high-revving and lightweight, while big blocks are known for low-end torque and sheer mass. The 5.7 Hemi kind of sits in the middle. It's an iron-block engine, which makes it pretty heavy compared to modern all-aluminum small blocks like the GM LS series.
The physical dimensions of the engine are also a bit deceiving. The cylinder heads on a 5.7 Hemi are quite large because of the way the valves are positioned to create that hemispherical (or semi-hemispherical) combustion chamber. This makes the engine wider than a standard overhead-valve small block. So, while the "block" itself might be small block in scale, the "total package" feels much larger. But if you were to line up a 5.7 next to a 426 Hemi or a 440 Big Block from 1969, you'd see the 5.7 is much more compact.
The Numbers Game: Displacement Matters
In the old days of the "Big Three" automakers, anything under 400 cubic inches was generally considered a small block. There were exceptions, of course, but that was the rule of thumb. The 5.7 Hemi comes in at 345 cubic inches. To put that in perspective: * The classic Chevy 350 (Small Block) is 5.7 liters. * The Ford 351 Windsor (Small Block) is roughly 5.8 liters. * The old Mopar 360 (Small Block) is 5.9 liters.
Since the 5.7 Hemi has less displacement than many of the famous small blocks of the past, it's hard to justify calling it a big block based on size alone. Even its bigger brother, the 6.4-liter (392) Hemi, is built on the same architecture. Even at 392 cubic inches, the 6.4 is still considered a "small block" design because it shares the same basic block dimensions and bore spacing as the 5.7.
What Actually Defines a Big Block?
To really answer is a 5.7 Hemi a big block, we have to look at what engineers actually mean by those terms. It's not just about the numbers on the side of the truck; it's about "bore spacing." This is the distance between the center of one cylinder and the center of the next.
Big blocks have wider bore spacing, which allows for much larger pistons and more displacement. Small blocks have tighter bore spacing to keep the engine shorter and lighter. The Gen III Hemi series has a bore spacing of 4.46 inches. For comparison, the old Mopar big blocks (like the 383, 400, and 440) had a bore spacing of 4.8 inches. That half-inch might not sound like much, but across four cylinders, it adds up to a much longer, beefier engine block.
The 5.7 Hemi was designed to fit into modern engine bays that have to account for crumple zones, steering racks, and complex suspension systems. A true big block would be a nightmare to package in a modern Challenger or Durango without making the car massive.
The "Hemi" Name and Marketing
Let's talk about the elephant in the room: marketing. Chrysler knew exactly what they were doing when they brought the Hemi name back in the early 2000s. They could have called it the "New Magnum" or just the "5.7L V8," but "Hemi" is a brand. It's a word that commands respect.
Because of that branding, the 5.7 Hemi gets compared to the big blocks of yore more than any other modern engine. You don't see people asking if a Ford 5.0 Coyote is a big block, even though it's a physically large engine because of its dual overhead cams. But because the Hemi name is so tied to the 426 Big Block, the question stays alive.
It's also worth noting that modern Hemis aren't even "true" Hemis in the strictest sense. The combustion chambers are more of a "polyspherical" shape now, flattened out slightly to improve emissions and fuel efficiency. But calling it the "5.7L Semi-Hemispherical" doesn't exactly have the same ring to it, does it?
Performance: Does It Matter What We Call It?
At the end of the day, whether you call it a small block or a big block doesn't change the fact that the 5.7 Hemi is a workhorse. It's been the backbone of the Ram pickup lineup for two decades, and it's powered some of the coolest modern muscle cars we've seen.
It produces the kind of torque that you used to only get from a big block. With the introduction of Eagle heads in 2009 and Variable Valve Timing (VVT), the 5.7 became even more efficient and powerful. It's got that "get up and go" that makes a heavy crew-cab truck feel surprisingly light.
Most enthusiasts will tell you that the 5.7 Hemi is the "perfect" size. It's small enough to be somewhat decent on gas (especially with the cylinder deactivation system) but big enough to do real work. It's the quintessential modern American V8.
The Verdict
So, if you're at a bar or a car meet and someone asks is a 5.7 Hemi a big block, you can confidently tell them it's a small block. It's a Gen III Hemi, designed for the modern era, with a compact block and 345 cubic inches of displacement.
But, if they want to argue that it feels like a big block or that it carries the spirit of the old 426, they aren't totally wrong. It's a heavy, powerful, iron-block V8 that has kept the Hemi legend alive for a whole new generation. It might not have the massive bore spacing or the "Elephant" footprint, but it's got plenty of heart.
In the world of modern engines, the "small block vs. big block" debate is slowly fading away as we move toward turbocharging and electrification. But for now, the 5.7 Hemi stands as one of the last great examples of the "small block" that could punch way above its weight class. Whether it's hauling a trailer over a mountain pass or doing a burnout in a church parking lot, it's doing exactly what a Hemi was born to do—regardless of what category we put it in.