We've see some pretty wild custom builds in the past, but this might be the craziest. One engineer thought it would be a good idea to swap a junkyard-sourced V-12 from a Ferrari 400i into his 1984 308 GTS using quad-valve heads from a Testarossa. This wouldn't be the first V-12-swapped 308 we've seen, so on the surface, it doesn't seem like much of a big deal. Where it got interesting, though, is when the builder realized the Testarossa heads he bought didn't bolt onto the 400i block. What follows is a mind-bending amount of custom fabrication to get everything to fit nicely, outlined in this 13-page Grassroots Motorsports forum thread.

Mke / Grassroots Motorsports Forum

Grassroots Motorsports forum user "Mke" claims he bought the Testarossa heads thinking they'd be an easy bolt-on piece. But it turns out none of the bolt holes or oil paths lined up. Instead of selling them and buying something that would fit better, he decided to cut and re-weld the heads so they'd fit to the 400i V-12 engine, fit bigger valves, and conform to the 308's tight engine bay. While that sounds ludicrous, the pictures provided by Mke on the thread show some impressive metal work, and videos uploaded to his YouTube account show the car in nearly road-ready condition:

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The engine now displaces 5.4 liters (up from 4.8 liters) thanks to an increased bore. There are titanium connecting rods from a 360 Modena, custom high-performance camshafts, larger valves, a dry-sump oil setup, and individual throttle bodies sourced from a Ducati 999 super bike. The builder estimates that once finished, the engine could be making more than 900 horsepower, which is just ridiculous. Power is sent to the rear wheels via a beefed-up 308 transaxle and a three-disc carbon clutch. Other notable upgrades include a custom-built pedal box to handle the brake setup from an F430, and a Chevy-sourced starter motor.

Mke / Grassroots Motorsports Forum

Of course, I'm just scratching the surface. Head on over to the Grassroots Motorsports forum thread to see how this 11-year old project became a reality. Even if you're not into Ferraris or engine swaps, the sheer amount of fabrication work done on this build is still worth a moment of your time.

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