Options for ditching this problematic carb. In the last few years of the CJ series and the first few years of the Wrangler YJ Jeep outfitted the 4.2L (258) 6 cylinders with an electronic carburetor referred to as the BBD. The Carter BBD is a two barrel carburetor that came in two variations, one is computer controlled and has a stepper motor on the back side. The computer controlled version was used after 1981. Both have similar problems and considering they haven’t been “new” in approximately 20 years alternatives are sometimes the best option to regain reliability and performance.
The BBD carb has a nasty reputation, most anyone that has owned a Jeep with one of these can relate. Sputtering, stalling, stalling at every stop sign and only running off idle. Very frustrating to deal with.
There are several popular alternatives; electronic fuel injection systems by Mopar, Howell, Holley and the home grown; carburetors by Weber and Motorcraft. We will explore the positives and negatives in all three types.
The benefits of fuel injection are well documented. Reliability, efficiency, and flexibility are some positive benefits to an electronic fuel injection system. Some negatives of these systems can be complexity and cost. Fuel injection systems inject the fuel into the airflow by means of a pressurized fuel system and electronic solenoid valves commonly called injectors. The injectors pass the correct amount of fuel as determined by the computer. The computer often uses several sensors to calculate this fuel mixture. Since the system is pressurized vapor locking is practically impossible and there is no fuel bowls to spill over in off-camber, incline, and decline driving conditions.
There are two different versions of fuel injection systems we will discuss here, Multi-port and Throttle Body.
Multi-port systems use injectors mounted in the intake manifold near the cylinder head port. These systems are regarded as generally more efficient than throttle body systems.
Throttle body systems simulate a carburetor and typically can mount in place of a carburetor. These systems have injectors mounted within the throttle body, which pass the fuel into the throttle body to mix with the air flow directly above the throttle plate.
Mopar - Mopar makes an EFI system (shown to the right) that is similar to the system found on the later model 4.0L engines in the following models Cherokee, Grand Cherokee, Wrangler YJ, Wrangler TJ. This system will require the largest installation time and cost the most but will usually yield the best performance gains and engine efficiency. This isn’t quite a fair comparison but a 4.2L carbureted 6 in a typical 80’s CJ made approximately 120HP, the 4.0L in the XJ was rated at 190HP. $$$$
Howell - The Howell throttle body system (shown left) includes all components plus a new 4.3L Chevrolet throttle body to convert a 2BBL CJ or Wrangler Jeep to EFI. This system replaces the carburetor and manual fuel pump, the original computer (if equipped) can be removed along with all the wiring associated with it. A new electric fuel pump is mounted on the frame in line of the fuel feed. Matt’s Jeep, an 84 CJ-7, has a Howell system installed with good results. The power difference and engine behavior is very distinguishable from the original set up. Matt no longer experiences stalling or stumbling when climbing hills on the trail. Howell offers an emission legal and off-road only version. See Howell Engine Developments for more. $$$
Holley – We get many questions about where to get this system. As far as we can tell Holley no longer offers a Pro-Jection system for the Jeep 6 cyl.
Home Grown – We have seen several write ups around the net detailing a less expensive conversion that gives you a throttle body system for less. This swap typically involves the use of a parts of TBI systems out of a vehicles equipped with a GM 4.3L V6, Typically a Chevy Blazer or GMC Jimmy. After reading many of articles detailing these swaps they seem do-able but are not for the impatient and/or technically challenged. Perform at your own risk! $$