DCOE:
Weber’s sidedraft DCOE has become legendary, but like many legends it’s largely misunderstood. While the DCOE has powered all types of race cars, from tiny 1000cc screamers to big honking V8s, it’s not necessarily a performance/racing carburetor.
The DCOE’s great strength, and great weakness, is that it can be infinitely customized. Every part of it can be swapped or adjusted to achieve the desired results. You can optimize torque, horsepower, economy, or any combination of them.
The downside is that it can require a lot of know-how and experience to do so. A DCOE may meet your requirements right out of the box, or it may not, depending on exactly what you want it to do.
From a design standpoint, the DCOE is somewhat like two single throat sidedraft carburetors sharing a single float bowl and throttle shaft. From that standpoint, they share some similarities with SUs. Most commonly a 45 DCOE is offered for MGBs, but the smaller 40DCOE is sometimes found. The 40 and the 45 DCOE share most parts, but the primary difference is in the venturis. DCOEs allow you to set the actual venturi size, something DGVs and SUs can’t do, and the 40 will accept very venturis, while the 45 while take very large ones. As a practical matter it doesn’t make much difference which kind you have on an MGB, as most B motors want a 34 or 36mm venture, which either type will comfortably handle.
While properly setting up a DCOE and all of its varied tubes and jets can be a daunting task, it does have several advantages over other carbs. Like the DGV, once it’s set up, it’s 100-percent reliable and requires little or no attention at all. And because of its modular nature, it can grow with your motor. With one set of jets and chokes, it can provide trouble free motoring on a stock motor. With another set, it can fully exploit the hottest B motors long after a set of SUs have been pushed past their limits.
It’s also a bit better made than SUs: The throttle shaft rides in bearings, so wear is virtually non-existent, and the overall casting and design is a masterpiece of smart engineering.
