1966-1977 Ford Bronco Engine - Stroking A Bronco

As for the carburetor, Holley has just the line to do the job with its Truck Avenger series. These are specially modified versions of the traditional performance carbs, built with off-road service in mind. Tech highlights include a special vent tube to prevent fuel spill-over, spring-loaded needle and seat valves for improved fuel inlet control, and a special metering block that prevents flooding even in extreme situations, up to a 40-degree approach angle, a 30-degree departure, or a roll. That's damned near any way but upside down. These carbs come in three sizes, from 470 to 770 cfm, and we went for the big one. The vacuum secondaries, and the Bronco's relatively light weight, go a long way to making such a large carb useable in this combination.

Those are the basics of how we arrived at this engine setup. With everything pondered over and thought out to the best of our ability, it was up to Speed-O-Motive to build it and then test on the dyno to prove its worth. We were on hand as Speedo's dyno operator Jake Harriston loaded the brute to the DTS pump, dialed in the baseline settings, and sparked it to life. With the open dyno headers, the 347 sounded sweet, settling into an idle that left no doubt that this was a bad boy. After an agonizingly long 30-minute run-in, we were ready for some noise with the imminent power pulls. With the torquey 347 topping the 400 mark in both horsepower and torque on the SAE scale, this thing more than doubled the factory gross power numbers. This kind of power is enough to stampede any Bronco.