6 Biggest GM Engines Ever Made

Car News Central counts down six of the biggest engines General Motors ever built, from cross-divisional big blocks to modern crate motors capable of 500-plus horsepower. Along the way, longtime GM owners weigh in with their own builds — including a stroked 541 cubic inch monster and a 455 doing duty in a boat. Watch to see which engine tops the list.

Ask a room full of GM guys to name the biggest engine the company ever built, and you’ll get a different answer from every corner — and most of them will be wrong. Some will shout displacement numbers they’ve never actually measured. Others will insist a boat motor doesn’t count. This video runs the tally straight, from a torque monster that once lived under the hood of a family sedan to a crate engine so absurd it makes 500-plus horsepower without breaking a sweat. One entry on this list still gets fistfights started in comment sections a decade after it left the factory floor. Which one survives to the top spot says a lot about what GM was actually capable of when nobody was watching the budget.

The BOP Big Blocks Nobody Talks About

For most of the muscle car era, Buick, Oldsmobile, and Pontiac each built their own 455-cubic-inch big block — related under the skin through a shared basic architecture, but engineered, tuned, and marketed as if they had nothing to do with each other. Viewers still argue in the comments about which BOP 455 hit hardest, whether it’s the Buick’s torque curve, the Pontiac’s breathing, or the Olds version featured prominently in this countdown. GM let each division chase its own personality with these engines for years, which is exactly why they still feel so distinct today even when parked side by side on a dyno stand.

⚑ Featured Gear

Start Car Conversations →

As an Amazon Associate I earn from qualifying purchases.

Why the Olds 455 Still Turns Heads

The Oldsmobile 455 shows up in this countdown for a reason: it was built for torque first and redline second, and it shows in how it pulls off idle. One commenter on the video runs his 455 in a boat, of all places, and swears the sound alone is worth the price of admission over any modern marine engine. That’s the kind of engine the 455 was in period road tests too — not a screamer that needed to be wound out to make its power, but a low-end bully that could move serious weight, whether that weight was a full-size Cutlass or a hull cutting through water, without ever seeming to strain.

The 496 Big Block’s Second Life

The 496 big block gets its moment here too, resurrected decades after its original run for builders who want big-block sound and cubic-inch bragging rights without chasing down and paying for a numbers-matching original casting. On the dyno stand shown in the video, it wobbles enough on its mounts to make more than a few viewers nervous in the comments, but the pull itself draws real praise as one of the meaner-sounding entries on the entire list, proof that aftermarket big-block architecture can still deliver factory-era drama.

Crate Power: The ZZ502 and 572

Two crate engines round out the modern end of the countdown: the ZZ502 and the 572. One owner in the comments who ran a ZZ502 describes it plainly as “a beast,” rated over 500 horsepower and over 500 lb-ft of torque across most of its usable RPM range — numbers that would have been unthinkable from a factory-built engine during the actual muscle car era, delivered here in a crate with an install manual and a warranty instead of a decade of tuning and machine work.

500 Cubic Inches and Counting

Not every big number in the comments came from the factory floor. One viewer describes stroking a 500-cubic-inch engine out to 541 cubic inches for a personal truck build, calling it “a great build” and describing the finished result as “a beast of a truck” in the same breath. It’s a reminder that GM’s biggest engines didn’t stop growing once they left the assembly line; enthusiasts have kept pushing the displacement ceiling higher for decades using aftermarket blocks, strokers, and cylinder heads that GM’s original engineers never had access to.

One Company, Five Nameplates, One Engine Plant

There’s a reason GM eventually created a dedicated Powertrain division: for years, each brand quietly borrowed engines from the others, and customers noticed and complained. A Pontiac could show up from the factory with a Chevrolet engine under the hood; a Buick might carry an Oldsmobile mill; a Chevrolet truck could run a GMC engine instead of its own division’s design. The mixing was common enough by the late 1970s that GM centralized engine production to keep the lineup consistent, a piece of corporate history that explains why so many “GM engines” from this era defy easy brand labels even today.

The Garage Culture Behind the Numbers

Ask anyone who’s spent real time in an engine bay about the culture around these builds, and you’ll hear the same joke repeated almost word for word: no mechanic worth trusting works without a cigarette dangling from his mouth, ash never quite falling no matter how long it burns. It’s a running bit in the comments on this video, but it points at something real — the shade-tree culture that grew up around big-inch GM engines, passed down from one generation of home builders to the next through exactly this kind of shop-floor humor.

Why These Engines Still Matter

What ties all six engines together isn’t a shared block casting or even a shared decade; it’s the fact that each one still commands genuine respect from people who’ve actually turned a wrench on one. Crate motors built last year and half-century-old big blocks get cross-referenced in the same comment threads, compared on the same terms by the same audience. That’s rare in the collector world, where old and new usually don’t share a conversation, let alone a countdown video and a comment section arguing across generations of hardware.

How Collectors Verify These Big Blocks

None of the claims made in a video like this one hold up without a way to check them, and that’s exactly why GM collectors lean so heavily on casting numbers and engine codes stamped directly into the block. A partial VIN derivative, a date code, and a casting number together can confirm whether a given 455 or 496 is actually what a seller claims it is, rather than a later replacement or a mismatched rebuild dropped in decades after the car left the factory. It’s tedious, unglamorous work compared to just listening to an engine run, but it’s the difference between a documented big block and a good story with no paperwork behind it.

Check out the full video above and let us know what you think in the comments.

Share your thoughts in the comments below.

Republished by Blog Post Promoter