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MG MGA - Weber Side Draft

I am putting together a 59 A and considering adding a Weber 45 DCOE side draft carb. to replace the SU's has anyone done this? and what advise might they have?

Thanks
Jeff
JK Mead

Jeff,

If you want to have fewer problems, KEEP THE SU's.

George Raham
[a TD spy]
G. L. Raham

Hi Jeff
I fitted a 45 DCOE weber on my MGA.

The main reasons being, the weber has far better throttle response and I was fed up with problems with the SUs (Leaking fuel) (Choke sticking) (ETC)
Plus I have a good knowledge of webers having used them for about 35 years. :-) so they do not fill me with fear.

I left the inner wing in place and went with a short manifold on the weber. This sill meant that the air filter was a tight squeeze. I fabricated a special air filter box but i also ran with a couple of socks on for a while without problems. It would be easier However with the inner wing modified.

The weber is not difficult to set up I believe (many disagree) so if you go with the weber or want more detail let me know.
Robert (Bob) Midget Turbo

I would recommend that you download a fascinating article (just 33000 words) titled "Tuning the 1800cc MGB". Just type that into Google or look for www.stirlingbritishmotoringsociety.org/files/mgbtunings.PDF You will need adobie acrobat to download it.
It has the most amazing technical detail on tuning a B-Series engine that I have ever seen.

I know you probably dont have an MGB engine in your car but the tuning principles are much the same.

Going back to your question, on page 13 (of 29 pages) it discusses carburetors in great detail.
The author states that the Weber DCOE has a better throttle response than SUs which gives the illusion of more power but, unless you are racing your car when improved throttle response is really important, "there is no worthwhile difference between them in terms of power output on the dynamometer readouts".

You may not agree(Robert) but it makes fascinating reading and it gives you lots to think about.

I must admit though that the DCOE both looks and sounds fantastic on an MGA.

Best of luck
Colyn
Colyn Firth

There is a good book that also covers the MGA here:

http://clancy.ch/Library.html (BMC book)

Or the factory Special Tuning book here

http://clancy.ch/Owners_Pack.html
dominic clancy

I've got a 45DCOE on an MGB. The car runs great, but I'm in the process of switching to a pair of HS6s. The DCOE was great when I was tuning the car. Being able to switch out jets in a few minutes, worked great. I was able to tune things first with an Innovate wide band o2 meter hooked up to a computer, and then on a dyno. Of course, I've got a bag of $200 of jets left over from the process.

There are several reasons I'm going to HS6s. I was never able to get the a/f mixture to keep from leaning out above 5500rpm. Also, the DCOE choke doesn't have any idle adjust, it's just adds fuel. Cold starting isn't a problem, but running between start and warm is a problem. Also, there's a new manifold that is supposed to improve high rpm airflow in the SU carbs.

As for why 45DCOE or HS6 instead of HS4? I had extensive head work done to improve breathing, and the guy who did the engine work thought I might need more than HS4s. I'd be curious to know how much difference in power/torque there is on my car between the three carbs, but not enough to put together a set of HS4s just for comparison.
Dave McCann

Hi Colyn

Why should I disagree. if you read my post I never spoke about extra power simply suggested it was more reliable than the SUs and that throttle response was better. In essence that is the same as the extract you refered to.

on the other hand It does help at higher revs unlike Dave in the post above I find the weber fuels high revs far better than the SUs, but it is a matter of opinion I would expect.

By the way I live in N Lincs (Near Scunny) where are you in S Yorks?
Robert (Bob) Midget Turbo

I used to love those Speedsport Tuning Books Dominic, I used one to modify my Hillman Imp engine in the early 70s and it went really well afterwards.

It looks like they could find an extra 6 bhp with a 45 DCOE on an MGB race engine back then as compared to SUs.

Sorry Robert, I kind of assumed that you would be a DCOE convert and that you would shoot my research down in flames!
I live 8 miles NE of Doncaster on the A19 so I am only 30min away from you. Email me if you are ever likely to be this way or let me know when I can use you as an excuse to give my car a run out!
colynfirth@msn.com
Colyn Firth

I suppose I should clarify. The DCOE didn't exactly not work at high revs. I had loads of fun. It felt like I had loads of power right up to the 6000 rev limiter on the ignition (electromotive). I have a non-stock cam, so that's some of where the high-rev power came from. And the DCOE works well with that. However, I just got tired of the other problems and didn't want to continue investing in little brass bits* until I could find a combination that gave a good A/F mixture all the way through.

*Brass bits: idle jets; main jets; air corrector jets; emulsion tubes; a few other types. I mostly tried a full selection of the first three, I never got around to trying different emulsion tubes or any of the other stuff)

I suppose the HS6s won't be much different. Still spending time swapping out needles, to find the one that gives good A/F mixture across the revs and loads.

JK: I'm all for trying new stuff, but you've not said what you were hoping to accomplish by changing carburetors. If it's just more power, I'm not sure just a carburetor change is the way to go. A cam and possibly some work on the head might be considered along with some carburetor changes (maybe just new needles). For bolt on instant power, it's hard to beat the supercharger. Believe me, I've spent far more than what you can get those things for and gotten far less power for my money.
Dave McCann

This thread was discussed between 22/01/2010 and 24/01/2010

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