For years the DGV was sold as a performance replacement carb for the
MG. Itís not. While it will produce almost as much power as a pair of
SUs, itís much less sportscar-like about doing it. Actually,
DGV clones were sold on about a gazillion different cars from
the factory, not because of their performance, but for their
other attributes: good economy and rock solid reliability.
The reason itís not really a performance carb
has to do with its basic design. The common 32/36 DGV
downdraft carb has two barrels, a 32mm barrel and
a secondary, 36mm barrel (which explains the 32/36 designation). An SUís
1 1/2 inch barrel equals 37.5mm, so both of the DGV throats
are smaller than a standard SU. The 32 and 36mm
throats together, though, are considerably bigger than the
Itís not just throat size, though. Under partial throttle,
only the smaller throat of a DGV is open. This contributes to itís
excellent economy, but does nothing for the thrill
of the ride. In fact until the secondary opens, DGVs are a bit
They do have many virtues, though. They are a
beautifully easy swap on any MG, even those with a brake
booster. They can be set up in no time flat (many work beautifully
right out of the box) and once theyíre set up, youíll never
touch it again. They stay in tune, donít wear out, and are one less
thing to tinker with as long as theyíre on the car.
Thereís actually several different types of DGVs available, differing
primarily in their choke type. The standard DGV uses a manual
choke. The DGEV has an electric choke, and the DGAV uses a
water choke. Choose the kind that suits you. Personally, I
think the electric choke is ideal. It works flawlessly every
time, and you never touch the choke again either. DGVs are ideal if you
just want to drive the car and not worry about your
carburetion, if economy is a concern, or if cost/ease if
fitment in a conversion is important.
A 38/38 DGS downdraft is now being offered for MGBs as well, which
offers throat sizes equal to the SUs and synchronous operation
of both throats. In theory, it promises the best of all
worlds, but field reports are scarce. Firsthand information is
Weberís sidedraft DCOE has become legendary, but like many legends
itís largely misunderstood. While the DCOE has powered all
types of race cars, from tiny 1000cc screamers to big honking
V8s, itís not necessarily a performance/racing carburetor.
The DCOEís 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 canít do, and
the 40 will accept very venturis, while the 45 while take very large
ones. As a practical matter it doesnít 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 itís set up, itís 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.
Itís also a bit better made than
throttle shaft rides in bearings, so wear is virtually non-existent,
and the overall casting and design is a
A brief mention of the clones is in order. These are carbs that
occasionally turn up on MGs or could be used on an MG with
ease. I say clones because all tend to follow one of the
preceding designs very closely, and could be matched to a
readily available manifold with little trouble.
The most common SU clone is the Mikuni, built
under a license from SU and usually fitted to older Japanese cars.
Theyíre not often found on MGs, and when they are itís
usually the result of some junkyard engineering, but theyíre almost identical to standard SUs and can work quite well.
The Holley 5200 is almost identical to the DGV
(and even closer to the Weber DFV), and was used on a ton of 4
and six-cylinder Dodge and Ford products, among other things. Be
careful with these Ė the castings are reportedly inferior to
the Weber part, and some have much smaller throats than the 32/36. Solex
2-barrel downdrafts have also appeared on MGs occasionally.
The DCOE has tons of clones, too many to list
quickly. Many can share most parts with the
Again, the point is that there is no ďbestĒ
carb. Think about
what you want out of your MG. How you drive it, how much you
like to tinker with it, what kind of economy you want, whether
you like a torquey motor or more on the top end, and make your
choice accordingly. All of them, properly set up, work well.
Ultimately, itís your MG, and your decision. Make it a wise and