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DCOE carb question

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Howard_The_Duck

Howard_The_Duck

Jedi Warrior
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Hey guys

I was tearing down my old S.U.'s the other day and realized that not only were the carbs the wrong ones for the car, but that the rear carb was all froze up.

My question is this: I have a Weber 45 DCOE carb/manifold that was given to me. Should I tear this one down, rebuild it, and use it on my car, or should I locate/rebuild the S.U.'s?

Also, what about rebuild kits for the Weber? I have found a site that sold a kit including the plastic float for about 50. If anyone here has bought rebuild kits for their Webers, I'd love to go with any outfits you recommend i buy the kit from.

Thanks guys!
Zack
 
The general wisdom is that a 45 DCOE is too much carb for a standard B engine. If you've ported and polished he head, oversized valves, over bore, uprated cam, it would be a good choice. The good thing about a DCOE is that it's infinitely tunable, the bad thing is that it's infinitely tunable, if you catch my drift.

My vote would be to rebuild the SU's, unless you've done the things to your engine I noted above. They are extremely well matched for a B engine. Sell the DCOE to recover part of the cost of the rebuild.
 
Was the DCOE you have already set up to run on a 'B? IF so, was the engine in that 'B substantially similar to yours? Are you sure it even needs rebuilding?

If you answer "yes, yes, no", then why not stick it on there and see how it runs? If nothing else, it'll keep you on the road while you rebuild your SUs. If you like it, you may decide to keep it. If not, sell it when you get the SUs back in service.

Too many people think putting a DCOE on an engine is going to create instant horsepower. Forget that - and least on a 'B. Only on the most heavily modified engines will that happen and, even then, a pair of HS6s would probably do just as well. For me, the primary attraction to the DCOE is that it's absolutely bulletproof once it's set up. Same is true of a DGV, but the sidedraft looks more sporting....

The DCOE isn't too much carb....but a lot of problems come because that are set up that way. Choke size is probably the most important factor in drivability. I run 34mm chokes in mine. 36mm is probably more common on a 'B, but are best with earlier high compression engines or slightly modified engines. 38mm is probably a mistake on anything but a race engine (same is probably true of HS6s). Too small and you lose top end. Too large and you lose bottom end - which is more important on a street car.
 
This is the story about the DCOE...

Dad bought a MGB about 15 years ago and it has languished in the salvage yard since. He bought it for parts as my mom's MGA Twin CAm's original engine got dumped when she was younger because it was too finicky, and a 1800 B motor was bolted in. (Randi still regrets that silliness :smile: )

The carb definitely needs rebuilding as evidenced by the amount of crud i had to pull out of it since it had open ram pipes :-\

I believe that the B this DCOE comes off of was prep'ed for racing of some sort, as evidenced by a few things ive noticed. On the other hand, my BGT is not race tuned.

The only reason I want a DCOE is because it is there, and I didnt want to shell out more money for S.U.s. The 80 dollar rebuild kits I bought still arent enough to get them functioning.

I do appreciate all of the input thus far though. Y'all have been extremely helpful.
 
As for the DCOE, it's possible that just a good cleaning might suffice - but....if it was originally set up for a racing engine, it'll almost certainly have you running rich, and with lousy low-end response. You can change the chokes, venturis, jets, emulsion tubes, etc - but that's a lot of money spent. And, odds are, you won't hit the corret set up on the first try. So that means more money spent on jets, etc.

If you REALLY, want to run the DCOE, at least begin with a configuration that is the recommended one for your 'B. That should at least get you in the ballpark. The risk is that you'll blow a lot of cash trying to get the DCOE right - and never be happy with it.

They're great carbs when they're right....but the SUs are a lot easier to get right because they are such a known quantity in this application.

You other choice would be to use a Weber DGV. Not as sexy as a DCOE, but just as bulletproof - and a very well known street conversion. It'll cost you quite a bit less than a pair of new SUs and, in the end, probably not much more than getting your DCOE correct....
 
Not a good idea to run DCOE unless you will do some serious racing. Please refer to the book written by Peter Burgess on how to tune an MGB.

DCOE have infinite adjustments and most importantly have NO provision for vacuum advance. A road car should always be running a distributor with vacuum advance because timing can be easily advanced alot with just a small trottle opening not the case with a strait mechanical distributor.

Here is a very nice article to read on:

https://www.sterlingbritishmotoringsociety.org/files/mgbtunings.PDF

An that's my take on it.
 
True, the carb has no provision for a vacuum advance port - but some of the manifolds do! Of course, you have to use a dizzy that's curved for the manfold advance...

I've got a vacuum advance 25D on my car with a DCOE. Vacuum advance port is on the rear intake runner. Port for the brake booster is on the front runner.

And it runs great...
 
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