This 1965 Mustang Grenaded Its Engine on Camera – Then a Facebook Marketplace Stroker Doubled Its Horsepower

8-Ball is a 1965 Mustang coupe that has been rebuilt front to back on camera – everything except the engine. When that finally let go, the replacement was a 331 stroker bought off Facebook Marketplace and advertised at 500 horsepower. Here is what a used-parts swap actually looks like when 1.4 million people are watching.

There is a specific sound a tired small-block makes right before it stops being an engine, and roughly 1.4 million people have now heard it happen to a black 1965 Mustang coupe named 8-Ball. The car had already been dragged back from the dead once. New paint. Rebuilt suspension. A four-speed Toploader swap. A posi rear end. The one major component nobody had touched was the motor that supposedly came with the car from the factory, and that motor is now scrap. What replaced it did not arrive from a crate program or a builder with a two-year waiting list. It came off Facebook Marketplace, and by the end of the video the owner describes the car as a completely new animal.

The Engine Everyone Watching Had Already Written Off

The video comes from TOM’S REFURB, a channel that has spent years documenting this one Mustang in unusually long form. This installment runs a full hour and two minutes, and it earns the runtime: the failure, the teardown, the used-engine hunt, the install, and every small problem that surfaces along the way all get screen time. The channel’s own framing is refreshingly blunt about what happened. The car’s “alleged FACTORY ENGINE finally bites the dust,” and the fix is a 331 stroker pulled off Marketplace and advertised as a 500-horsepower combination. Worth noting up front: the creator states in the description that all driving footage was filmed in Mexico on closed courses and edited with CGI and AI, so treat the on-screen theatrics as entertainment rather than a road test.

The Comment Section Called It Before the Engine Did

The reaction in the comments is where the story gets interesting. With more than 25,000 likes and nearly a thousand comments, the top responses are not arguing about horsepower numbers at all. Several viewers immediately pointed back to a detail they had flagged in earlier videos – a double-stacked head gasket – and claimed vindication when the engine finally let go. Whether that was the actual culprit is not something the video declares outright, but it tells you something about this audience that they were tracking a gasket stack-up across multiple episodes. Others were simply along for the ride, and a striking number of comments were from people who credit the channel with teaching them enough to start wrenching on their own cars.

⚑ Featured Gear

Start Car Conversations →

As an Amazon Associate I earn from qualifying purchases.

A 331 Off Facebook Marketplace, and the Math Behind It

So what exactly is a 331? It is a stroker version of Ford’s small-block, built on a 302 block with a longer-throw crankshaft. The common recipe uses a 4.030-inch bore paired with a 3.250-inch stroke, which lands the displacement right around 331 cubic inches. It is one of the most popular budget stroker combinations in the Ford world precisely because it uses a block that is everywhere, tolerates pump gas well, and adds real cubic inches without exotic parts. The 500-horsepower figure attached to this particular engine is the seller’s claim, not a dyno sheet, and anyone shopping used engines should treat those numbers the same way.

Doubling 200 Horsepower Is a Lower Bar Than It Sounds

Even with a healthy dose of skepticism applied to that claim, the “doubled the horsepower” framing in the title holds up against the factory baseline. A 1965 Mustang with the two-barrel 289 was rated at 200 horsepower gross. The four-barrel version carried a 225-horsepower rating, and the legendary Hi-Po 289 – solid lifters, better exhaust manifolds, a Holley four-barrel – topped the range at 271 horsepower gross. Those are gross ratings from an era with famously generous measurement standards, so real-world output was lower. Against any of those numbers, a well-sorted 331 stroker is a genuine transformation rather than a marketing line.

Ford Built 410,260 of These Coupes – That Is the Whole Point

It is easy to forget how ordinary a 1965 Mustang coupe was when it was new. Ford built 559,451 Mustangs for the 1965 model year, and the hardtop coupe accounted for 410,260 of them. Ford had originally projected something closer to 100,000 units a year. The Mustang instead became the most successful new-model launch American automakers had seen in decades, and the coupe was the body style doing most of the heavy lifting.

Why the Cheapest Body Style Became the Builder’s Body Style

That volume is exactly why a car like 8-Ball exists today. Fastbacks and convertibles command the money and the auction headlines, which leaves the hardtop as the affordable entry point – the car you can buy rough, learn on, and modify without a collector’s committee looking over your shoulder. It is the same logic that drives most first-generation Mustang builds, whether the answer is a used stroker or something far more modern. For the other end of that spectrum, our deep dive on Coyote swapping a classic Mustang covers the packaging headaches that come with dropping a current-generation V8 into a 1960s engine bay.

The Gearbox That Was Already Waiting Behind It

The transmission behind that new engine deserves a mention of its own. The Toploader was Ford’s in-house four-speed, introduced for 1964 to replace the BorgWarner T-10 and built at the company’s Livonia, Michigan plant. The name comes from the access plate on top of the main case rather than on the side, a layout that made the case noticeably more rigid than its competitors. Ford used the design across its lineup until 1973, and it remains the gearbox of choice for exactly this kind of build. Fitting one – along with a posi rear – before the engine upgrade turns out to have been the right order of operations.

Why 1.4 Million People Sat Through a One-Hour Engine Swap

What makes this video work is not the horsepower. It is that almost nothing about the build is aspirational in the usual sense. The replacement engine came from a stranger on Marketplace. The problems get solved on camera, in real time, with visible frustration. Nothing is edited into effortlessness. That is the opposite of most build content, and it is clearly why the comment section reads the way it does – one viewer described lining up an automotive job after two years of watching, another credited the channel with the confidence to fix a struggling 1980s Mercury.

The Warning Buried in the Comments

The audience also pushes back where it counts. Multiple commenters urged subframe connectors and a properly fitted cage before the car goes any faster, which is a reasonable thing to say about a unibody coupe from 1965 that just gained a large amount of power. That mix – genuine enthusiasm paired with genuine concern – is rarer in car content than it should be, and it says a lot about the relationship this channel has built with the people watching.

Watch the full video above and let us know your thoughts in the comments.