The Weber 45 DCOE is a popular choice for MGB owners looking to unleash a bit more power in the admittedly rather prosaic (but reliable) B-Series engine. This was the carb of choice among factory entries and racers in the heyday of the MGB, and coupled with the reliability inherant in the design, it powered the B to many finishes above more tempermental entries by other sportscar manufacturers of the time.

Combined with a large-bore block and a modern high-flow head, the 45DCOE can really make a difference on the dyno. Whether or not this conversion is cost effective considering the expense and the return in HP, is up to you.

Under normal driving conditions, it is my opinion that a well-maintained pair of HS4 or HIF4 SU carburetors is just as good, if not better than, a 45DCOE, considering the complication and expense that tuning these race-application carbs can require. If you do not have the expertise or equipment (such as a wide-band oxygen sensor and rolling road) to tune these carbs properly, you may be chasing after settings endlessly - the number of variables in tuning these carbs is large and requires an understanding of the theory of operation.

The settings listed here are a starting point only, from which specific modifications will most likely be required.

Weber 45 DCOE Initial Settings for MGB

Notes

When fitting a 45DCOE to the B series engine, a special manifold will be required. The carb itself is mounted on synthetic rubber O-rings ("Thackeray washers") which absorb vibration and prevent the air-fuel mixture from being disturbed. A steady rod should be made up and connected to the rear engine plate.

Your Weber conversion will be most worthwile if you combine it with cylinder head modifications, a free flow exhaust system and a good air filter setup like K&Ns. Tuning is a complex affair and best done on a rolling road.

More information can be found in MG World No.7 (Oct/Nov 1998) and in Lindsay Porter's DIY Guide (available in the Shop.)

Weber 45 DCOE Diagram