MGB & GT Forum

side draft Weber pros and cons?

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zedvictor1 Avatar
zedvictor1 Steve L
Albion, WA, USA   USA
"Weber high performance DCOE side draft carburator" that's what the ad says for the 77 MGB.
I mostly see the downdraft Webers and know most here prefer the twin SU's to those . . . and anything to the ZS. Is the side draft a good match for the engine? I've read it is more expensive and gives better performance.
Would I be grinning every mile or pounding the steering wheel in frustration?

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golf bernard lanigan
montgomery al, USA   USA
1976 MG MGB "The B"
WASTE on a normally configured engine !

Be Coming Avatar
Be Coming Kelvin Dodd
So. Calif., USA   USA
Stephen. The DCOE is completely adjustable, so it can be configured for any level of engine performance from stock to wild.

BUT! Since you can only bolt one onto the MGB, rather than having one choke per cylinder, so the DCOE becomes very limited.

You can either have increased power at maximum rpm. Or you can have good low end torque at low speed and good mileage. You can't have both.

I've run DCOE carbs on MGs for many thousands of miles. The way to make them work effectively for street use is to choke them down with 33mm chokes. This reduces the upper performance level to less than that of twin 1 1/2" SUs. If you are only driving between 2,000 - 5,000 rpm, then the carb works fine and the accelerator pump gives a snappier acceleration when compared to the SUs.

If you are looking for power above 5,000 rpm, then you have to use larger chokes in the Weber, which does reduce low speed efficiency, fuel mileage and torque.

Unfortunatly, you can't have it both ways.

Personally for all around use, the twin 1 1/2 SUs are the best performing set up.


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balloonfoot Avatar
balloonfoot Gold Member Lloyd Faust
Southlake, TX, USA   USA
The noise level of a Weber drives me crazy....Weber carbs have the most intake roar of any carb ever invented. Fun the first day....gets old fast.

Law of Logical Argument - Anything is possible if you don't know what you are talking about.

"Anyone with an intense emotional interest in a subject loses the ability to observe it objectively: You selectively perceive events. You ignore data and facts that disagree with your main philosophy. Even your memory works to fool you, as you selectively retain what you believe in, and subtly mask any memories that might conflict."

underdog Avatar
underdog Jim Underwood
Pittsburgh, USA   USA
1972 MG MGB
1980 Triumph TR8 "Fabulous Trashwagon"
1999 Chevrolet Corvette "Darth Vader"
1999 Chevrolet S10 "Spare Change"    & more
I prefer the Mikuni PHH 40 but they don't sell em as a kit anymore. So it's a moot point. Ocassionally they turn up used.

And I love the intake sound. Sort of reminds me of the old F1 engines of the late 60s. Different strokes & all I suppose.

Edited 1 time(s). Last edit at 2009-11-22 08:06 AM by underdog.

O, ON, Canada   CAN
1967 MG MGB GT "Maggie (GT From Hell)"
The DCOE is a god carb. It needs to be adjusted to the size and airflow/fuel mix requiremnts of the MGB engine. What this means is taking a 45 DCOE and effectively making it a 32to36 DCOE.

Because of the spacing of the carb throttles, you do not get a straight shot into the MGB siamesed intake ports. This means you need to run a manifold with a curve in the runner. People will argue that this causes fuel separation due to the high port velocities and centripetal forces. The result being that the inboard (cyl 2&3) cylinders are going to run leaner than the outer two. Maybe maybe not. I think that is more a race car issue.

The DCOE offers so many possible adjustments, it is almost impossible to find the correct one if you are new to the game. You really need some ind of a yardstick; either a dyno or an O2 sensor. If you are at all budget conscious, the 50 bucks you keep tossing at components gets old and you learn to live with a "good enough for the girls I go out with" set-up.

When looking to iprove the performance of an internal combustion engine, you start by finding the restrictions to airflow. In the case of the MGB, this is obvioulsy the head. Stock SU carbs are well up to the task of feeding the MGB all the air it could possibly need. The DCOE is capable of feeding it WAY more and hence needs to be chocked back itself to match the MGB needs. Most people leave them too big.

Got one on the "GT From Hell". Love the looks. Chocked down to 36 mm on a full ported and cammed engine. Still too much, but I learned to live with it and the lousy mileage. Cause it looks and sounds cool!


lewk Avatar
lewk Silver Member Keith Lewis
Cambridge, ON, Canada   CAN
Want a side draft Weber? Here you go, Weber 45 MCHH. Use original manifold and be rid of the ZS.

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wdp Avatar
wdp Silver Member w p
Calif, USA   USA
1953 MG TD
1958 MG MGA 1500
1966 MG MGB
1972 MG MGB GT
Also, you would need to run a non-vacumn advance distributor. If the setup is already on a running car the tuning is already done.

bob pantano Avatar
San Antonio, TX, USA   USA
I bought by 80 back in 1997 with the side draft DCOE...It's been perfect...No complaints

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Fairfield, CA, USA   USA
In reply to a post by Be Coming Stephen. The DCOE is completely adjustable, so it can be configured for any level of engine performance from stock to wild.


I'll quibble on the “adjustable.” There's nothing you can go in there with a screwdriver to "adjust" except the idle screw.

You can adapt the things to any level you want. This entails at least partial disassembly and replacement of parts.As well as knowing what parts to replace and which of the many, many different specifications of each part you want to use.

1973 Pale Primrose Roadster. A nice 10-footer!
SUs, Datsun 5-speed

zedvictor1 Avatar
zedvictor1 Steve L
Albion, WA, USA   USA
Thanks everyone. I wish my expertise was slightly better than almost nil.
I guess it's foolish to buy a car at the beginning of winter (3 inches of snow here this morning) but this one seemed rather good.

RAY 67 TOURER Avatar
RAY 67 TOURER Ray Marloff
Fort Bragg, CA, USA   USA
1967 MG MGB "My Girl"
They are, indeed, excellent carbs. I ran one for 10 years on my B before installing a supercharger. Yes, they are a pain to set up, requiring 2 of every part when calibrating. This quickly gets rather expensive as every part seems to cost $50. Once you find the right combination of components, they do run quite well, but the stock twin SUs are hard to beat. RAY

pralahda Avatar
pralahda Wayne Barrett
NSW, Australia   AUS
1955 BMW r25
1965 MG MGB MkI "The Red Rat"
As people here possibly already know...I would never part with my 45 DCOE...and I run 38 chokes....

great all round performer...but really assists when the cam hits up at around 5500.

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