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What’s Under the Hood of This 1966 Ford Bronco Will Shock You!

Posted in Features on April 6, 2018
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Honestly, we don’t even know where to start with Doug Brown’s 1966 Bronco. At first glance it looks like a clean, uncut Early Bronco that spends most of the time in the garage. The paint is perfect, and the skinny BFGoodrich tires and American Racing wheels really complete the look. Then he fires up the engine, and it is immediately obvious that there isn’t a 289 under the hood. Actually, it has a four-cylinder engine: a 4BT Cummins turbodiesel. Doug bought the engine off of eBay with 60,000 miles on it and installed it in his Bronco as part of a four-year restromod that started back in 2009.

We’re just getting started. The Cummins is backed by an NV3500 manual transmission rowed by a JB Custom Fab shifter. This is a modern five-speed manual with a hydraulic clutch linkage and easy shifting. Doug rows the gears on a regular basis, as this Bronco is his daily driver.

“It gets about 24 miles per gallon on my 20-mile drive to work,” he tells us. “I’ve put about 40,000 miles on it since I swapped the engine in.”

As if that weren’t enough, the NV3500 is mated to an Advance Adapters Atlas II transfer case with a 3.8:1 low-range ratio. This allows Doug to tip-toe through trails like the Rubicon and Hell’s Revenge in Moab. The Bronco has received a few battle scars along the way, but Doug takes it all in stride. It seems like a small price to pay for a vintage 4x4/daily driver/rockcrawler all in one!

The engine bay is absolutely perfect, from the paint to the hydroboost brakes to the 4BT engine that is clean enough to eat off. The engine came out of a bread truck and has been left stock for reliability. A Speedway Motors aluminum radiator and custom fan shroud keep it cool, while the engine breathes through an airbox from a Duramax, of all things.
The 1966 Bronco originally came with a Dana 30 axle, but it was replaced by a stock-width Dana 44 filled with 3.50 gears and an ARB Air Locker. If the gear ratio seems high to you, consider that the torque peak of the 4BT occurs at 1,600 rpm. Chromoly axleshafts route power out to the MileMarker hubs.
The heavy diesel engine is supported by 2 1/2-inch coil springs from Tom’s Bronco Parts and CAGE extended radius arms. They are assisted by Bilstein 7100 remote-reservoir shocks. A 2-inch body lift wasn’t necessarily required for the 33-inch tall BFGoodrich Mud-Terrain KM2 pizza cutters as much as the tall 4BT engine.
The rear axle is a 31-spline Ford 9-inch with an ARB Air Locker and 3.50 gears. A Ruff Stuff Specialties pinion guard bolts to the front of the third member and protects the driveline yoke and U-joint. The axle is suspended by leaf springs from Tom’s Bronco Parts and Bilstein 7100 monotube shocks.
Doug Brown built the bumpers himself out of 1/4-inch aluminum. The rear bumper has recessed LED backup lights and a trick spare tire carrier. The pivot is from Chassis Unlimited, and the carrier holds not only a spare but also a Hi-Lift jack and a complete spare hub and brake assembly.
The rear seat of the Bronco was jettisoned in favor of storage space. Under the factory roll bar, two big 5-pound fire extinguishers flank an ammo can and a small toolbox. Note how both are secured to angle iron with ratchet straps so they don’t go through the windshield.
Despite the perfect paint and uncut rear fenders, this Bronco actually gets wheeled. It has been through the Rubicon and to Moab. The biggest limitation is that the body sticks out farther than the tires.
Doug built the aluminum front bumper out of 1/4-inch-thick aluminum and fitted it with a Warn Zeon 10 winch with synthetic cable. The bumper maximizes approach angle and matches the lines of the classic Bronco.
Doug built an aluminum skidplate for the 23-gallon BC Broncos fuel tank that feeds the Cummins engine. The 3-inch stainless exhaust routes around the fuel tank and dumps behind the rear axle. Despite the 4BT’s reputation, Doug’s engine doesn’t belch a bunch of black smoke.

Tech Specs
1966 Ford Bronco
Engine: Cummins 4BT diesel
Transmission: NV3500 5-speed manual
Transfer Case: Advance Adapters Atlas II
Front Axle: Dana 44 with 3.50 gears and ARB Air Locker
Rear Axle: Ford 9-inch with 3.50 gears and ARB Air Locker
Springs & Such: Tom’s Bronco Parts coil springs and CAGE extended radius arms, Bilstein 7100 shocks (front); Tom’s Bronco Parts leaf springs and Bilstein 7100 shocks (rear)
Tires & Wheels: 255/85R16 BFGoodrich Mud-Terrain KM2s on 16x8 American Racing Ansen Sprint rims
Steering: 76 Bronco power steering box, Flaming River steering column, Extreme Custom Fabrication tie rod and draglink
Other Stuff: Custom aluminum bumpers, Warn Zeon 10, tire carrier with complete hub and brake rotor, Speedway Motors radiator, BC Broncos 23-gallon fuel tank, Duramax air box, ARB twin air compressor, Vanco hydroboost brakes, Ruff Stuff pinion guard, H4 headlights, aluminum intercooler, JB Custom Fab shifter and boot, Wild Horses Highlander hood, Bestop seats, Dakota Digital gauges, MileMarker hubs

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