The Weber DGV was originally designed for a 6-cylinder European Ford. It is quite tuneable and extremely reliable, making it a very popular carb to retro-fit on a great many engines, including those found in out LBCs.
The DGV is a dual-barrel downdraft progressive carburetor. When cruising, only the 32 mm bore is employed, giving good economy. Under load, the second, richer 36 mm bore opens up to supply additional power.
Jetting is readily available and is easy to change, in order to dial in the carb for specific engines. The carb is available in either manual choke, or electric automatic choke (DGEV) or water temperature automatic choke (DGAV) models. (There is also a synchronous-throttle with larger bores (DGS) for higher-output engines.)
However, when Weber originally designed the carb, they had no idea inkling of the vast number of applications the carb would eventually be used on. The carb is ideal for engines over 2.0 liters, but with a bit of tinkering, it is eminently suitable down to little A-Series displacements. The idea is to change some of the fuel curve behavior, so that everything happens at lower air flow volumes than the carb was designed for. While that may sound quite technical, it is actually very simple, once someone else (me) has done the brain work.
When installed on an MGB, DGVs are notorious for an off-idle "stumble" or "dead spot" and a slight hesitation when accelerating quickly.
The first is caused by the progression, or off-idle circuit, giving up before the main venturi starts to supply fuel. This is solely an effect of less air being drawn in at low RPMS by a smaller engine that carb is expecting. We will fix this by extending the effective range of the progression circuit to the point where enough air is being pulled in that the main venturi will take over.
The second issue is caused by a too-small accelerator pump nozzle. Blame emissions laws or conservative engineering pools. The carbs just seem to come set up for a more pedestrian style of driving. The lively little MGB really appreciates a little bit more zip.
