Off Road Carburetors - High-Carb Diet-TechPosted in How To on August 1, 2004 Comment (0)
Despite what the pro-fuel-injection crowd may like to believe, scads of enthusiasts still 'wheel carburetor-equipped rigs and do so to great results. Boasting concepts such as owner adjustability and engine-specific tuneability, carbs continue to earn a reputation as efficient fuel mixers. But when state-of-the-art fuel-injection systems seem to be available for nearly every application out there, and when you consider the traditional issues involved with running carbs off-road, it's easy to determine why so many have forgone the carburetor for electronically controlled fuel systems.But don't go tearing that carburetor off the manifold just yet. Believe it or not, there are still plenty of reasons why carburetors are considered to be an effective means of fuel delivery in 4x4s.
The foremost reason we can think of as to why one should run a carburetor rather than fuel injection is perhaps the largest concern to any enthusiast: It's cheaper. Many others reasons still exist and weigh heavily in deciding what type of fuel delivery system is the right choice for your vehicle. In general, carburetors are easier to install, virtually maintenance-free, easy to clean and rebuild, easy to troubleshoot or trail-fix, and in many cases, simply less hassle than fuel-injection systems.
A number of carburetor options exist for off-road applications, including off-road-specific units such as the Holley and Edelbrock offerings, and custom-modified and -tuned Webers and Rochester Quadrajets available from BFIC in Burbank, California. The off-road-specific carburetor is a unique breed as it represents a recent trend in the aftermarket to address the needs of 4x4 enthusiasts. With built-in modifications designed to correct the inherent negative issues involved with using carbs off-road, these types of units are offered to provide bolt-on-and-go performance.
The following information was compiled to give you a better idea of the existing carburetor options available from the aftermarket. Whether your rig is still equipped with the factory carburetor, an inefficient carb designed for street applications, or even a problematic fuel-injection system, the right off-road carburetor is out there to effectively increase your vehicle's performance.
Holley Truck Avenger
More than just a remodeled street/car carburetor, the Holley Truck Avenger uses proven design and technology mated with specific features and components intended to enhance its off-road performance. This 670-cfm four-barrel carburetor is designed from the flange up as an off-road carburetor, without the typical stall or fade-out characteristics long associated with carbs when attacking steep hill climbs or side hill trails. Said to provide flood-free operation on inclines as steep as 40 degrees and 30 degrees in off-camber situations, the Truck Avenger uses a new fuel-metering block and a new one-piece metal vent tube to eliminate fuel spillover during extreme maneuvers. The Truck Avenger features a dichromate finish and is owner-adjustable within its secondary fuel system and choke mechanism for those running highly modified engines.
Edelbrock Thunder Series AVS
Possessing many of the same impressive features as the proven and dependable Performer Series line, the Edelbrock 650-cfm Thunder Series AVS Carburetor is designed specifically to meet the challenges of hard-core off-road use. Spring-loaded needles and seats ensure a consistent fuel supply when traveling through rough terrain, and the fuel chamber is side-mounted, so it's less likely to flood or stall-out during steep hill climbs. The float levels are preset at the factory, but Edelbrock's unique Qwik-Tune adjustable secondary valve allows for rapid adjustment without the need of tools. Other features include a manual or electric choke.
Equipped with either manual or electric chokes, the Road Demon Jr. is offered in three sizes and features side-hung floats to eliminate fuel spillover. The Road Demon Jr. is compact in design, making it ideal for use in vehicles where carb clearance is an issue, such as Jeeps and Toyotas with V-8 conversions. The Concentracast venturi and aero-flow air entries are designed for better driveability and performance. Other attributes include float bowls with sight glasses for safe and easy float-bowl adjustments and Max-Density cast metering blocks to maintain accurate tuning. All Demon carbs are wet-flow-tested and baseline-calibrated at the factory and are shipped with a detailed tuning manual. Carburetors are available in 525, 625, and 725 cfm to fit many differ-ent applications.
Capable of flowing as high as 930 cfm, the Predator Carburetor works strictly off the air demand of the motor and meters the fuel in relationship to that demand. This action is a result of the Predator's variable venturi air doors, which permit only the predetermined amount of air and corresponding amount of fuel to enter the intake manifold. This allows the engine to be neither under-carbureted nor over-carbureted, offering the most responsive performance possible for practically any driving situation. The Predator's flow and idle capabilities make it ideal for fueling 300ci to 500ci engines and will permit idle speeds as low as 800 to 1,200 rpm. While it's generally not as fuel-efficient as other types of carbs, the Predator offers an abundance of low-end torque, making it ideal for off-road applications. The Predator carburetor can also be mounted so that the fuel bowl points forward, which greatly addresses engine stall when the front of the vehicle ascends an obstacle.
The Redline Weber line of carburetors draws on years of proven off-road race experience to produce the horsepower and dependability needed to meet the harsh demands of off-road use. Carburetor kits are available to suit a wide number of 4x4 applications, including Jeep, Suzuki, Nissan, Land Cruiser, and Toyota trucks and 4Runners. The 32/36 DGV-series progressive and the 38 DGAS-series synchronous carburetors are ideal replacements for the carburetors on the 232ci and 258ci Jeep six-cylinder engines. Designed to be used on stock engines, the 32/36 model is said to deliver as much as an 18 percent increase in horsepower over stock and a 10 to 20 percent increase in fuel economy. The 38 DGAS is well-suited for use on modified engines, where increased performance takes precedence over fuel economy. It features a larger fuel-delivery system and the calibration necessary to handle the broader range of improved performance. Similar-series carburetors are available to improve performance in Toyota and other applications as well. All Weber carburetors are said to offer an easy installation, low initial cost, trouble-free maintenance, excellent driveability, increased fuel economy, and improved performance. Kits include a baseline-jetted carb, an adapter plate to the stock intake manifold, a complete linkage kit, and a chrome or stock air filter.
BFIC: Custom Carbs For Off-Road UseSpecializing in carburetors, fuel injectors, and other fuel system components since 1965, BFIC in Burbank, California, knows what it takes to make a carburetor perform well off-road. The company offers a full line of rebuilt and modified carburetors to suit a variety of applications. Using its carburetor-specific build sheets, BFIC can produce a carb built around the engine and vehicle in which it'll be installed. The company takes all factors into consideration, including engine modifications, drivetrain, vehicle use, and performance goals to achieve the desired results. According to BFIC, virtually any carburetor can be modified to meet the demands of off-road use. This includes factory-style carbs such as the Carter YF and BBD models and others not known for their off-road prowess. This is excellent news for vehicles that must meet smog requirements in emissions-controlled states. BFIC applies a varying degree of modifications to each carburetor to address issues such as jetting and low-speed fuel delivery to ensure that each unit will meet the demands of the application. The company also offers expert installation and precision-tuning and can supply all the necessary components to accompany its custom carburetors.