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MG MGB Technical - weber dcoe 45 problem

Greetings!

Does someone have the have the correct float settings for this carb with brass floats (I already checked the archives)?
I'm having the following problem which I think is an issue related to an incorrect float setting: Driving above 3500 RPM for more than about 5 seconds leads to what sounds like fuel starvation where the engine starts dying until I let off the throttle for a couple of seconds. The fuel pump is at 3lbs pressure and the filters are clean so delivery is fine. The Weber book I have does have settings but not specifically for the MGB.

If you can help, I would appreciate it - thanks!

Paul
Paul Tonizzo

If you've got a model number from the top plate (like "45DCOE-13"), I have a sheet somewhere from the service kit that lists the settings for them all. I think it's carb not car specific.
Steve Postins

BTW has the car been running OK on the carb until now? If not, do you know the jet sizes? Just thinking that your problem is around the point that the main jets take over. When you back off you may be moving back to the progression circuit and when you accelerate up to speed you will be dumping fuel in from the accelerator pump, perhaps giving your few seconds of smooth running.
Steve Postins

Could it be the carb is not properly soft mounted on the manifold? Are you sure it's the carb and not something else like the electrical system?

If you're out near Markham and you get stuck email me off list if you'd like, I may be able to help. I've got a newer 45DCOE on my B and it seems to be setup pretty well. Thirsty, but it pulls strong under all conditions.
Mike Polan

Is it just me, or does there seem to be a rise in
folks experiencing fuel delivery problems at the
close of every winter, or onset of spring?

Anyway, to answer your float level question:

I don't know if this applies to the newer Type 128
(Made In Spain) 45DCOE - but for the "Classic"
(Made In Italy) 45DCOE-9, 45DCOE-13, or similar...

Measured distance from top of float to bottom
(mating) surface of carb lid:

Closed = 5mm

Open = 13.5mm

Stroke = 8.5mm

Adjusting to acheive these specs is by trial & error.

First measure; then take apart and carefully bend
the float stop tabs to suit using needle-nosed
pliers; assemble & measure again. Repeat as
needed.

==========

Having said that...

What size main jets are you using?

I ask, because the mains come into use at around
2700-3000 or so (depending on manifold vacuum,
cam timing, etc.).

Stock MGB = 145

For hot street, try = 150

(these are initial tuning recommendations, only)

===========

What fuel pump are you using?

A stock SU works fine for most hot street duty.

At higher revs, it isn't pressure that matters so much...it's volume.
Daniel Wong

My carb is a 45DCOE9.
Engine is a pretty stock 1800 3-main.
jets are:
choke 32
emulsion tube F16
main jet 135
air jet 155
pump jet 45
idle jet 55F8
aux venturi 3.5

Got these settings directly from Weber and they are a world better than what I had when I first got the carb.
The pump is an aftermarket unit that delivers 22-28 G.P.H. at 4-5.5 P.S.I. I have a pressure regulator lowering it to 3 lbs. Playing with the pressure does nothing for the problem (except cause the carb to leak if it's too high!).

>When you back off you may be moving back to the progression circuit and when you accelerate up to speed you will be dumping fuel in from the accelerator pump, perhaps giving your few seconds of smooth running.

I get continual good running until I try to exceed the 3,500 RPM mark so I don't think this is it.

>Could it be the carb is not properly soft mounted on the manifold?

Possibly - do you know the procedure I should follow? I have the o-ring type gasket. BTW, thanks for the help offer - might take you up on that!

thanks for the help, Gents!
Paul Tonizzo

I'd try stepping up to a bigger set of main jets as it
sounds like you're starving for fuel at mid-range
revs - just as when they should phase themselves
into duty.

My 2¢.

Daniel Wong

This thread was discussed between 20/04/2004 and 21/04/2004

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