Some folks take the whole automotive hobby thing pretty dang seriously, but at the end of the day, these four-wheeled contraptions are meant to be fun – especially when there’s a Big Block on command under your right foot. Such is the case with this 1978 GMC Jimmy, which is now sporting a 572-cubic-inch monster under the hood, courtesy of former Hoonigan employee Zac Mertens. Now, we’re getting behind the wheel of this high-powered rig with the following feature video.
Unsurprisingly, the truck has undergone extensive modifications over the years. Zac shares the backstory of purchasing the truck for $3,000 in 2020 – originally intended as a pre-runner build, the GMC Jimmy was left to deteriorate in the desert before Zac rescued and transformed it. Despite some patina and minor rust, the truck retained a solid foundation for Zac’s vision.
The star of the show is the 572 cubic-inch big-block engine built by Smeding Performance. The engine includes a Dart Big M block, forged rotating assembly, AFR heads, and a Holley Dominator ECU, delivering 733 horsepower and 733 pound-feet of torque on the engine dyno. Recent upgrades include a port fuel injection system, a 4500 flange manifold, and high-performance injectors. The GMC Jimmy also features an overhauled cooling system, a pulsed fan setup, and Vintage Air’s air conditioning system.
Throughout the video, we get a sense of the garage-built nature of this GMC Jimmy, which retains a “rough around the edges” charm while performing impressively on the road.
The truck’s transmission is a beefed-up Gearstar 4L85E, paired with 4.56 gears and reinforced axles, making it capable of handling the engine’s immense torque. Despite maintaining stock-style suspension with off-road springs and Bilstein shocks, Zach admits the setup is soft and the chassis is unreinforced, leading to a “sketchy” driving experience.
Of course, that’s all part of it. The truck excels in delivering raw, unfiltered fun, with a chunky torque curve and the ability to perform burnouts and slides effortlessly.
The video concludes with a spirited drive on the street, showcasing the rig’s rowdy nature. Check it out for yourself right here:
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