The Legend of Boomhauer - Zac Mertens’ MF-Equipped C10

July 30, 2020 | Team MagnaFlow

The third-generation Chevrolet C10 “square-body” debuted in 1972 for the 1973 model year as a full sheet metal redesign of General Motors' tried and true pickup. Over the years, these trucks garnered quite the fan base, becoming popular among builders and enthusiasts. Large aftermarket support and a cult following allowed the C10 to live on in highly customized forms, making it one of our favorite platforms.

To learn more about one of the baddest C10s around, we sat down with Zac Mertens of Hoonigan. Over the past year, Zac built a 1974 C10 nicknamed Boomhauer, upgrading it with a host of performance parts and, of course, a custom exhaust with the MagnaFlow touch.

Zac acquired his C10 after a visit to fellow Hoonigan Vinny Anatra’s garage. On a shelf, he saw a ‘Moon Eyes' footprint gas pedal. When he asked about it, he learned that it was from Vinny’s old C10. Vinny told Zac, “if you build a square body, you can have the pedal for your project.” Zac already needed a truck to cart around his Harley Davidson motorcycles, so Zac decided to take Vinny up on his offer.

Strip Down

Like most things in life, sometimes you have to put in some work before you get to have fun. In the case of Zac’s C10, that meant stripping down the pickup to get it ready for a host of new parts. He began by first removing major engine accessories from the stock Chevy small block, like the air filter, carburetor and distributor.

Next, he removed the truck's interior components as well as the entire engine and transmission, - which came out as one unit, finishing the teardown with the removal of the front clip. This revealed the frame and resting place of the C10’s new engine, but before putting the new unit in, some suspension work was needed.

Front Suspension

After stripping the frame of the old stamped steel suspension components and giving it a fresh coat of paint, Zac installed a new QA1 coil-over suspension kit. The QA1 hardware adds tubular front control arms and high travel springs along with an upgraded sway bar with polyurethane bushings. The result was a considerably more athletic C10 than its brick-like body would suggest. This also allowed Zac to dial in the perfect ride height, framing his new set of full-face Detroit Steel Smoothie wheels.

A new steering column with a super-quick ratio box from Squarebody Syndicate finished off the handling upgrades at the front end.

Rear Suspension

At the back, the C10 received a matching QA1 coil-over suspension kit as part of a slightly more involved install. After removing the truck-bed, Zac and some friends notched the frame to give the rear axle a place to go under suspension compression with the lowered stance.

The QA1 kit includes bolt-on subframe supports to make this notching rather easy, while simultaneously adding mounting points for the heavily revised suspension. Zac’s C10 acted as a test bed for QA1’s new torque arm coilover kit, forgoing the four-link setup most aftermarket suppliers opt for. New components included coil-overs, a rear sway bar, adjustable truck arms, a C-notch bracket, a panhard bar, and the noted torque arm that reduces suspension binding for more predictable behavior at the rear axle.

Engine and Transmission

Under the hood, Boomhauer got a healthy dose of power by way of a Texas Speed 434ci Gen 4 LSx V8. The engine is essentially an aluminum block LS3 resleeved with Darton steel units, replacing the factory iron sleeves. Additional upgrades to the new power plant included a Texas Speed sheet metal intake manifold, PRC 260cc chambered aluminum cylinder heads, a BFD stroker camshaft, and forged internals, all topped off with ARP hardware

Fuel is delivered by a Holley 450 LPH fuel pump and regulator routed with Earl's Performance Pro-Lite -8AN hoses and fittings. Zac also updated the ignition system with a new setup from MSD and overhauled the cooling system with a Frostbite LS swap three-core aluminum radiator with 14-inch SPAL fans to keep things cool under the harshest of conditions.

When asked how he would describe the character of the new Texas Speed mill, Zac had one word, “savage.”

“For a [naturally aspirated motor], you can beat it up without it overheating and still get 20 mpg if you baby it. It’s reliable, but at the drop of a hat, it's absolutely wild. There’s torque all through the rev-range and pulls to 7400 rpm.”

When all was said and done, Boomhauer put down around 530 horsepower, making it one potent pickup.

The Texas Speed engine is mated to a GearStar-Pro 4L80E Level 4 automatic transmission with a Yank 10-inch torque converter with 3400 rpm stall speed (this being the engine RPM at which the torque converter transfers the power of the engine to the transmission). This higher stall speed helps the C10 swiftly get off the line. When asked why he chose an automatic transmission, Zac told us that his C10 was “built to be a daily driver,” so he wanted to be able to cruise in LA traffic and have it be comfortable.

The 4L80E gets power to the new Currie 9-inch rear end by way of a QA1 carbon fiber driveshaft, which as Zac pointed out, “gives you some pretty awesome bragging rights.” However, there are performance gains as well. The new carbon unit reduces rotational mass and drivetrain power loss, and Zac notes that “even at high speeds, there's absolutely no vibration. The driveshaft balanced-out much better than the factory one.”

Brakes

Speed is all well and good, but if you can’t bring things to a stop, you’ve got yourself a real problem. To make sure Boomhauer’s stopping power matched its horsepower, Zac opted for a set of Wilwood Superlight 4R big brakes with Wilwood Pro spindles along with a Wilwood master cylinder and proportioning valve. As the name suggests, the new Wilwood calipers have four-pistons, which added serious anchors to this almost half-century-old pickup. The spindles allowed the calipers and rotors to bolt up with ease, while further reducing weight at the front axle.

Exhaust

To put the boom in Boomhauer, Zac had the crazy idea of outfitting his C10 exhaust system with a set of NASCAR boom tubes. In MagnaFlow terms, we would describe their interior sound level as very, very aggressive and their exterior sound level as very, very, very aggressive.

Zac was actually offered the original stock car parts on Instagram and couldn’t resist. “They basically work like a megaphone,” he explained. “Initially, it was like amplifying open headers.”

After driving around for a couple of days, he decided that the exhaust was awesome but far too loud. Welding in a set of MagnaFlow Race Series resonators helped quiet things down just enough while still preserving the truck’s menacing sound.

To make a neighborhood-friendly version, Zac also turned to MagnaFlow. His alternate setup is constructed with MagnaFlow’s mandrel-bent 3-inch piping and uses two 11-inch MagnaFlow straight-through mufflers. He plans to install a set of race-bred Magnaflow V-band clamps in the future to make switching between the two setups a bit easier.

Finishing Touches

Zac explained that “the idea of Boomhauer was to keep the old service fleet look because it was still going to be a work truck,” while making it better to drive and a lot faster. On the inside of the C10, a Vintage Air air-conditioning system and Dakota Digital gauges added some modern conveniences. Otherwise, you’ll find mostly stock parts installed with good condition units sourced from the Squarebody Syndicate classifieds.

A set of Michelin Pilot Sport 4S tires may be one of Zac’s most important additions because, as he noted, “they make really gnarly smoke clouds” – perfect for the Hoonigan 'Burnyard.’

Of all the square bodies out there, Boomhauer certainly makes it high on our list of favorites. This pickup is the perfect mix of old-school muscle, modern performance, and endearing patina, plus that rumbling exhaust note is sure to excite any enthusiast. We’d like to thank Zac for walking us through his exemplary build and we’re glad that MagnaFlow components had a part in making it all come together!