A Subaru flat-four engine is one of the most distinctive powerplants in the automotive world — that signature rumble, the low center of gravity, the horizontal cylinder layout that defines the brand. So naturally, a crew of Russian mechanics decided to saw one in half and weld it back together as a conventional inline-four.
Garage 54, the YouTube channel known for automotive experiments that range from ingenious to certifiably unhinged, took two Subaru boxer engines and performed what amounts to open-heart surgery. They split a boxer down the middle, stood the two cylinder banks upright, and placed them side by side to form a single inline configuration. The result is an engine that has no business existing, yet somehow turns over.
The fabrication was anything but simple. Because a boxer-four’s cylinders oppose each other horizontally, standing them vertical and lining them up effectively doubled the engine’s length compared to the original. That meant a second donor engine was needed just for the crankcase, which was cut and welded to the first. The cylinder heads got the same treatment — two stock Subaru heads fused into one elongated unit.
The rotating assembly required similar creativity. Two factory camshafts were welded end to end, carefully oriented to maintain proper valve timing. The crankshaft is a Frankenstein piece built from two stock cranks joined by custom-fabricated coupling tabs.
Unlike a production inline-four, where the block itself cradles the crank during assembly, this cobbled-together engine offered no such luxury. Getting everything aligned and secured was, by the builders’ own admission, a delicate affair. One happy accident emerged from the conversion: a Toyota 1JZ timing belt fit the reoriented engine perfectly. That’s the kind of serendipity that keeps garage hackers going.
The oiling system tells you everything about how far this project strays from convention. Instead of a single oil pan hanging beneath the engine, this inline-four has two oil pans — one on each side — because the original boxer’s lubrication paths were designed for a horizontal layout. Making that actually function is a problem Garage 54 has deferred to a future video, along with intake and exhaust manifolds, plumbing, and accessory pulleys.
The engine isn’t running yet. But it is fully assembled, it rotates freely, and it represents a level of mechanical problem-solving that most professional engine builders would find either impressive or deeply offensive.
The obvious question — why turn a boxer into the most common engine layout on the planet — doesn’t really have a satisfying answer. Garage 54 has never operated on logic. This is the same channel that tried running a diesel on gasoline and bolted together a V16 from chainsaw engines.
The point was never utility. The point was seeing if the metalwork, the timing, and the physics could be wrestled into cooperation.
What they’ve proven so far is that a Subaru boxer-four is, at its core, just four cylinders, four pistons, and a crankshaft — and that the arrangement is more negotiable than Fuji Heavy Industries ever intended. Whether it will actually fire and sustain combustion is another matter entirely. But for a pair of hacksawed crankcases and some ambitious welding, the thing turns. In the world of garage engineering, that counts as a win.
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