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1969 Bronco: Propane-powered Agility

Posted in Features on November 28, 2016
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When Robert Warke rolls into a station to get fuel, heads turn. His bright yellow ’69 Bronco rumbles like an open-class desert racer at idle and sits atop 42-inch Goodyear Wrangler MT/Rs. It’s hard to miss. But what’s a little confusing to first-time observer is he gets it filled at the propane filling station, not at the gas pumps.

Robert’s propane-fueled 408ci stroker started life as a circle track race engine designed to run 6,500 rpm “all day long” while making north of 500 hp. The solid-roller cam has 0.590-inch lift, the heads are CNC-ported Canfield High-Port 2.08s, the rods H-beam with ARP main studs on the stroker crank. The JE pistons give it a 12:1 compression ratio, which helps fire off the propane being fed through dual 425-cfm Impco four-barrels. JBA headers and a Flowmaster muffler handle the exhaust.

That’s because the rumble of the exhaust comes from a 408ci Ford stroker built for circle track racing that Robert converted to run on propane. The engine, which Robert says “turns 6,500 rpm all day,” cranks out north of 500 hp thanks to a heavily modded block and heads stuffed with some of the best racing parts offered for a balanced-and-blueprinted, stroked-out 351. He designed and plumbed the propane fuel system from the dual-chamber 23-gallon tank in the cargo area to the dual Impco 425-cfm carbs sitting atop the Edelbrock high-rise intake feeding the CNC-ported Canfield heads.

Dune running and rockcrawling requires a lot of suspension travel, and Robert achieved it in the front by fabricating shock hoops and mounting dual 14-inch ORI struts to control the CBM Design’s radius arms.
The 42-inch Goodyears and Dynatrac ProRock 60 steering components are easily aimed thanks to a PSC XR Series hydro steering system. The ram and hoses are well protected by heavy-duty steel plate.

Keeping all that power in a rock-solid package so he can run the Oregon Dunes, Moab, Hammers, and challenging trails around the Pacific Northwest, Robert spent an enormous amount of time engineering the rest of the drivetrain and suspension. He rewelded every seam and filled every hole in the chassis, then set out to fabricate radius arms for the front and a four-link rear 5 1/2-inch suspension controlled by a combination of ORI struts and King coils. Underneath the rear ultra-long-travel suspension sits a shaved 14-bolt diff with Chevy 1/2-ton disc brakes, a Detroit Locker, 5.38 gearing, and Artec Industries truss. An ARB Air Locker-equipped Dynatrac ProRock 60 handles the front chores, turned by Artec high-steer arms and PSC Motorsports hydraulic steering.

The interior of Robert’s yellow propane burner is all about safety and information. The custom center dash is full of Auto Meter gauges and toggle switches control the Bronco’s electrical components from lights to fuel pump to seat heaters.

The interior is just as trick, with keyless ignition, custom Auto Meter Sport Comp gauges, a perfect dash from a ’66 Bronco, custom center switch/gauge panel, remote marine-style wiring and circuit breakers, 1 3/4-inch-diameter cage, and five-point racing harnesses to keep both passenger and driver secure in heated, high-back buckets.

Robert, the owner of CBM (Crazy Bronco Man) Designs, in Oregon City, Oregon, confesses he’s always changing things up on the Bronco he’s owned for 20 years. “I can’t leave certain things alone or just as they are. I want to see how far we can take the Bronco to the extreme, all the while still looking like a vintage Ford Bronco.” We think he’s accomplished that goal.

Good suspension travel and great traction with a ton of power make it easy for this yellow demon to rip up just about any giant pile of sand it encounters.

At A Glance

Vehicle: ’69 Ford Bronco
Owner: Robert Warke
Stomping grounds: Oregon City, Oregon
Build time: One year – this time around

Engine: Ford 408ci V-8 stroker
Transmission: Modified Ford C4
Transfer case(s): Advance Adapters Atlas 2
Low range ratio(s): 3.0:1
Crawl ratio(s): 39.7:1
Front axle/differential: Dynatrac ProRock 60, 5.38 gears/Detroit Locker
Rear axle/differential: Shaved GM 14-bolt, GM 1/2-ton disc brakes, 5.38 gears/ARB Air Locker

Front: 5 1/2-in CBM Designs, CBM radius arms, 14-in ORI struts
Rear: 5 1/2-in CBM Designs four-link, 12-in King coilovers
Steering: PSC Motorsports hydraulic

Tires: 42/14.50R17LT Goodyear Wrangler MT/R
Wheels: Custom 17x9 Fuel Off-Road Anza

Lighting: Forward, rear, underbody
Armor: Custom 12-point rollcage, custom rock sliders, custom front bumper, custom brushguard, custom rear bumper, custom belly cradle, custom skidplates
Cool stuff: Modified chassis, custom gauge panel, marine wiring with circuit breakers, custom propane fuel tanks, integrated onboard air, body wrap

The custom 23-gallon propane tank in the cargo area of Robert’s ’69 bobtail are filled by a connection (bottom right corner) that is the same type as used in motorhomes. He added an air coupler in the same location to ease airing up tires. The rear bumper and cage are custom designed by CBM Designs.
The shaved 14-bolt rearend runs 5.38s, has an ARB Air Locker, and 1/2-ton Chevy disc brakes. It also utilizes Currie Antirock sway bars.
Heavy-wall tube protects the Atlas 2 transfer case and Art Carr-modded C4 from rocks and allows some rub room as you can see from the scrape marks. The transmission uses a reverse manual valvebody and is built for 750 hp.
Robert made up the Bronco’s wiring harnesses using marine-grade materials and running them all to marine-style circuit breakers mounted in a stainless steel box on the driver-side kick panel. Each breaker is lighted so it’s easy to see if any are offline.
High-back buckets have been in the classic bobtail for a long time. The seats and the rollcage are about the only things Robert hasn’t changed in the last couple years.
A hot-rodded Warn 8274 winch handles any pulling duties Robert may need to address, while Warn H4 lights supplement the stock Bronco headlights. The front bumper, nerf plates, and skidplate are by CBM Designs. The paint job is actually yellow vinyl wrap done by OC Signs near Robert’s shop. Tires are 42x14.5R17LT Goodyear Wrangler MT/Rs mounted on 9-inch-wide Fuel Off-Road Anza wheels.
Propane filling is done via an RV-style connector to the 23-gallon fuel tank. The air fitting feeds from an ARB onboard air system and is used for refilling tires.
The custom center dash is full of Auto Meter gauges and toggle switches that control a wide range of things including lights, fuel pump, and seat heaters.
Underneath all the plumbing is a 500hp-plus 408ci stroker powered by propane. The engine started life as a circle track race engine designed to run 6,500 rpm for long periods of time. Propane is fed into dual 425-cfm Impco four-barrels.
PSC XR Series hydro steering and dual 14-inch ORI struts handle the majority of the front suspension and steering duties.
Robert runs 12-inch King coilovers on the CBM Designs’ rear trailing arms and remote mounts the reservoirs behind the seats so they get maximum cooling.
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