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Do Not give up on the DGV Weber.....

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borjis

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After reading several posts and other websites about upgrading from SU's to the Weber Downdraft DGV only to have a hesitation when you stomp on the pedal that seemed incurable, I was beginning to think I should have stuck with SUs.

Well, a lot of people bashed the DGV (it doesn't work) no doubt in the passion/anger of having to sell the weber and go back to SU's that don't have the problem.

I'm here to confirm the DGV is an excellent carb for your MG.

Researching into it further I found an article by someone saying a hesitation with a DGV means its improperly jetted for your engine....that someone was spot on correct!

It seems that .050 and .055 primary idle jets are whats usually installed by weber. These will most often be the cause of hesitation in MGA and MGB motors.

Upgrading to a bigger jet, then adjusting your idle mixture is the key.

After reading about this I told my Dad who restores british autos for a living. One of his customers MGA had been fitted with a DGV and they were about to go back to SU's when I let him know what I found.

This MGA had a .050 idle jet. They installed a .055 and the problem completely went away.

I had read that even a .055 on an alpine (1800cc) was not enough and you'd still have hesitation. Thinking that the problem was cured on the MGA (1600cc) with a .055 I figured I'd try a .060 since that fixed the issue on the alpine sized motor being the same as the mgb at 1800cc.

That was a correct assumption. I pulled a .055 out of my DGV, replaced it with the .060 started it up. This was interesting because now the car would not start without the choke engaged. It would always start before without the choke. After warming it up, I stomped on it and there was some hesitation but not nearly as much as before.

I then adjusted my mixture and found it had been originally turned out 1.25 turns. I adjusted it to 1.5 turns (idles perfectly at 900 rpm now too) then stomped on it.

Hesitation bye bye!

I hope this helps anyone else out that was in my situation.

The DGV is a great carb and when properly jetted/tuned runs very nice on the MG engines.
 
This is NOT rebuke, rather an opinion: My objection to the DGV is not whether it can be jetted to run smoothly. It can. The issue is that it's a downdraught design, progressive two barrel. Manifold design to get the mix to the valves with SU's or a sidedraught DCOE is just more desireable, IMO. We could get into allsorts over laminar flow, volumetric efficiency et-al. But if the plan is to get the mixture in and out of the chambers with efficacy, a straight line beats ninety degree turns every time.

...and aesthetically, well... /bcforum/images/%%GRAEMLIN_URL%%/jester.gif
 
The 38/38, which is not progressive, I believe, is supposed to be a much better carb for the B than the 32/36 progressive that nearly everyone is referring to when they talk about the DGV. Doesn't solve the right angle the air has to take, but at least it is better sized for the B application.
 
I like my "Outlaw" 38/38(DGES) is NOT progressive as you say lawguy. It makes better exhaust sound(thru my ANSA) as well as better power with no hesitation as compared to my old DGV. Webers are made to be tuned and if your engine is different from the standard in any way, you probably need to spend the time to do it.t's why racers like them but unless you're a tinkerer, you won't get the best performance...
 
interesting about the 38/38 not being progressive. I might upgrade to that sometime.

Will the 38 DGES fit on the same intake manifold for a 32/36 DGV?

I don't disagree about the more direct route that a DCOE or SU would take and that they do look more attractive. /bcforum/images/%%GRAEMLIN_URL%%/smile.gif

But I'd rather have a DGV down draft than a stromberg side /bcforum/images/%%GRAEMLIN_URL%%/smile.gif
If I had to choose between those two.
 
they both fit the same manifold and I agree, the weber is a definite upgrade over the zenith/stromberg.
 
Does the DGES fit the DGV manifold? --- MAYBE...

The mounting studs are the same but some DGV manifolds don't have a large enough hole for the 38 butterflies since when fully open they do intrude into the manifold space. If they don't fit, it's time for the Dremel grinder!

P.S. Don't forget to check the gasket too!
 
Good eye, Craig. The gasket can be a real puzzlement if not taken into consideration on install.
 
Hello Borjis,

I'm sorry but your statement "upgrading from SU's to the Weber Downdraft DGV" is misleading, how can a complicated fixed or compound choke carburettor match a pair of simple progressive choke instruments, particularly for driveablilty. I concede that the DCOE style horizontal Weber will give a few more BHP at peak revs on a tuned engine over the S.U.s but there is little in it.

Alec
 
piman said:
Hello Borjis,

I'm sorry but your statement "upgrading from SU's to the Weber Downdraft DGV" is misleading, how can a complicated fixed or compound choke carburettor match a pair of simple progressive choke instruments, particularly for driveablilty. I concede that the DCOE style horizontal Weber will give a few more BHP at peak revs on a tuned engine over the S.U.s but there is little in it.

Alec
Click to expand...


Are you implying that the DGV is inferior to an SU?
 
borjis said:
piman said:
Hello Borjis,

I'm sorry but your statement "upgrading from SU's to the Weber Downdraft DGV" is misleading, how can a complicated fixed or compound choke carburettor match a pair of simple progressive choke instruments, particularly for driveablilty. I concede that the DCOE style horizontal Weber will give a few more BHP at peak revs on a tuned engine over the S.U.s but there is little in it.

Alec
Click to expand...


Are you implying that the DGV is inferior to an SU?
Click to expand...

My opinion is that:
1. The DGV is technically inferior(slightly) to the twin SUs in that it is a compromise for owners who don't want to fiddle with twin carbs. A certain amount of performance is lost because of this.
2. The DGES betters this because of its non-progressive butterflies so that performance won't be lost.
3. The DCOE, as Alec says, may give better performance on race engines because of its tuning capability.

Just remember, 1-1/2" SUs are 38mm venturis. DGVs are 32mm/36mm and DCOEs can be tuned with many different venturi sizes...
 
/bcforum/images/%%GRAEMLIN_URL%%/thankyousign.gif /bcforum/images/%%GRAEMLIN_URL%%/bow.gif
 
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