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Old 11-04-2019, 04:20 PM   #1
fatcatbestcat
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Default 140 carburetor conversion; DGEV vs DCOE

I finally got around to emptying my car of all the parts that came with it, and got the time to pry the airbox apart. Inside, I found a hole in the air filter element, and underneath that, a rodent nest. I was probably going to replace my SUs later anyway, but now that they're literally full of crap, and all the linkage is rusty and barely functional, I think I might do that now.

I'm looking to make some kind of semi-performance daily driver-esque vehicle, and the two carbs I'm considering are as follows:

A Weber DGEV (probably a 36/38): I guess the logic being that it's reasonably cheap and I can reuse my current choke lever for the weber's electric choke. Probably better for daily driving, since I live in a colder climate.

DCOEs: Probably a racy setup and I'm not so sure about using these on the street... I'm also not sure that it will give me any kind of worthwhile power gain over the DGEV... I'm also not convinced that this would run well in cold weather.

Any advice would be helpful.
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Old 11-04-2019, 04:25 PM   #2
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Doesn't sound like you are wanting anything too snorty - so I'd suggest keeping with the SU's. They're better than the usual DGV swap you see on a pushrod Volvo. And the DCOE's are a bit much if you aren't really going to use what they can do above and beyond what the SU's can do.

My DCOE's are really snorty in cold weather, sneezing, snorting, don't really run well until the engine compartment gets a little heat soak in it. And it takes a magical combination of choke, throttle pumps (1.5, no more, no less) and holding the throttle the right amount open (no more no less) for it to start in the cold. But they are glorious in action and really add a lot to a well modified engine.
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Old 11-04-2019, 04:32 PM   #3
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Doesn't sound like you are wanting anything too snorty - so I'd suggest keeping with the SU's. They're better than the usual DGV swap you see on a pushrod Volvo. And the DCOE's are a bit much if you aren't really going to use what they can do above and beyond what the SU's can do.

My DCOE's are really snorty in cold weather, sneezing, snorting, don't really run well until the engine compartment gets a little heat soak in it. And it takes a magical combination of choke, throttle pumps (1.5, no more, no less) and holding the throttle the right amount open (no more no less) for it to start in the cold. But they are glorious in action and really add a lot to a well modified engine.
I'm fixing on taking the SUs off and taking a good look at them tomorrow, but I need to make sure the manual choke and all the linkage is actually engaging...

I'm probably going to leave the rest of the engine mostly stock... I have a B20F head that I'm going to have machined, from there, probably a cam, header then intake/carb.
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Old 11-04-2019, 04:44 PM   #4
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The SU's fitted as stock really were a bit over specced on what the engine was capable of using. If you pep it up a modest amount you might need new needles. But Volvo was not choking the HP down with an undersized carb setup.
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Old 11-04-2019, 04:49 PM   #5
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The DGEV is 32/36 with progressive linkage. You can also get a 38 DGES with synchronous linkage.

There's also a 40 DFI with synchronous linkage but they aren't made anymore.

Making The Right Choice 32/36mm Progressive or 38mm Synchronous

DCOE's are nice but like John said, you need engine upgrades to take advantage of them.
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Old 11-04-2019, 10:27 PM   #6
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Da Truuf is DCOEs were OEM carbs on plenty of cars with ancient ignitions and nobody complained..Mainly Italian cars and they tolerate more fiddle than Norte Americanos...
The trooof is also that any advantage over the VERY nice DGMS-DGES rally only comes if you go minimum 45 DCOE and at least 36mm venturis..

40s would give maybe a paltry 5% more Haitch Peas....max..and for the money and bother for max 5 measly % , why bother with 40s?

But 45s. you have the foundation of real fun...
And I've daily driven and lent my little 1740 or 1815 iron head V4 to dozens of people and they work just dandy even in rush hour stop and go traffic with a fairly "amusing" camshaft (around 310 degrees duration, 11.4mm valve lift, 106 lobe centers..and moderate 10.8 to 11:1 compression (static comp)

DGV 32/36 I wouldn't bother with as, aAGAIN, AFTER COST AND TIME AND FAWKIN' AROUND YOU NEVER GET THE SECOND BARREL UNTIL THE FIRST SIDE, THE ABSURDLY SMALL LITTLE WEENIE 32MM WITH THE MICROSCOPIC 26MM VENTURI IS 2/3s OF THE WAY OPEN (fawk caps lock), why bother??
The yummiest 38/38 DGMS (manual choke) you get both side from zero on up...Wise choice.
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Old 11-05-2019, 12:26 PM   #7
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I already have a DCOE manifold... I guess I'll just keep looking for 45 or 48 DCOEs then.
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Old 11-05-2019, 12:37 PM   #8
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I would think that JohnV would agree, but who knows, but 45's aren't going to add anything to the party on an otherwise mostly stock motor. 40's are enough to feed it.

But 36mm chokes are as big as you can go in 40's, so they're just limited in future potential if you keep piling mods onto the motor itself. 45's can certainly use small chokes and be set up to feel a mild motor, and then expanded for future fun.

Only point is that if you don't have big future plans, and you find a set of 40's for considerably less than a pair of 45's (which is possible) then think about getting them. They'll make all the right noises, have the razor-sharp throttle response, and outperform a set of SU's. Just not (when supported by a well-rounded set of engine mods) a set of 45/48's.

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Old 11-05-2019, 01:02 PM   #9
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IMO, the main reason carbs get a bad rap is because the loudest critics are the ones who tried to run huge carbs on a stock engine. I'd always choose DCOEs over a DGEV, but they'd be 40s with probably 32mm chokes for maximum mid-range fun .
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Old 11-05-2019, 01:12 PM   #10
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I did try the 36's on my PV when it was still a bit more stock (stock head, D cam, header) and they did NOT work. Boggy, you could be careful with the throttle and keep them happy in a transition to WOT, but it was mostly a farce. I went back to the 32's and stuck the 36's on a shelf. Until later when I put the R-Sport head, VV81/S/etc cam, roller rockers, 4:2:1 header, etc. Then, and only then, did the 36's work.

And I probably need 45's on it at this point for maximum aytch peas, but the 40's were just really cheap ($300 plus a smidge for shipping, plus manifold and linkages) and they still make the PV hop up and go in a very amusing manner, so it's just a matter of complacency and inertia now.
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Old 11-05-2019, 01:24 PM   #11
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Going from a pair of SUs to a DGEV would be a downgrade. If you’re having trouble with them and don’t want to fart with it, send them to one of the several people who rebuild them.
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Old 11-05-2019, 02:00 PM   #12
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I'll throw in my two cents here as well.

Stick with SU's and get them up to snuff if you are running anything close to a stock B18/B20. The SU's are much more user friendly for someone wrapping their head around carburation. The Weber's are going to be expensive and difficult to setup correctly (not that rebuilding SU's is cheap especially if throttle shafts are involved) but I highly doubt you'll notice much gain and will be disappointed when they don't produce perceived results.

Yes, Webers look cool and make cool noises (I to acknowledge these were factory on many performance cars of the era), but so do a nice cleaned up set of SU's. The only thing you'll really notice between the two honestly is tip in from a stop or cruising as the Webers massive accelerator pump circuit reacts quicker then the pistons in the SU's.

If you do go DCOE do not go any bigger the 45's, that's already pushing volume limits unless you have high compression and all the supporting mods. If you go too big on carbs and associated choke size your low end will suffer and feel worse then a poorly tuned SU. With my experience with these engines, because they are not particularly peaky or high revving, is to slightly undersized for the street as most guidelines seem to be geared toward high performance or race. Doing this will get your best all around performance (torque), instead of that peak horsepower (high RPM).

In a nut shell, bigger is not better for the street. Keep it simple.
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Old 11-05-2019, 04:51 PM   #13
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It is either SU's or DCOE's nothing much else worth bothering with
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Old 11-06-2019, 12:39 PM   #14
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Thanks for your input, everyone.
A friend let me drive his 4-cylinder Monza, which had DCOE 40s on a custom manifold. The iron duke revs about the same as a B20, is pretty similar in displacement and the car weighs about the same. It took a little bit of effort to start in the cold weather, but the throttle response was great on the built motor. That was pretty much enough to convince me that I'll go with DCOEs if the SUs don't work out.

I intend to run my B20 pretty stock; D Cam, B20F head (which I'm going to have shaved down a bit, the goal being 10.5:1 compression), and probably some valve springs, so the 45 probably would be a bit overkill
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Old 11-12-2019, 05:00 PM   #15
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Quote:
Originally Posted by John V, outside agitator View Post
Da Truuf is DCOEs were OEM carbs on plenty of cars with ancient ignitions and nobody complained..Mainly Italian cars and they tolerate more fiddle than Norte Americanos...
The trooof is also that any advantage over the VERY nice DGMS-DGES rally only comes if you go minimum 45 DCOE and at least 36mm venturis..

40s would give maybe a paltry 5% more Haitch Peas....max..and for the money and bother for max 5 measly % , why bother with 40s?
Good to know. That's what i thought, i've experienced the same thing. Now i want my DGAS back on or use the DHLA 40 Dellorto's with enlarged venturis just as throttle bodies en put EFI and an ECU on it.
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Old 11-12-2019, 05:21 PM   #16
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When we were racing back in the early part of this century. I used to see a guy with his 144. It had twin DGEV webers on it. He did that by using the twin manifold adapters for Triumph six cylinder engines and bolted those to the stock Volvo intake. They ran well on the B20 providing good low end torque and economy while having more top end than the single conversions.

The carb swap that no one does or knows about.

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Old 11-12-2019, 05:36 PM   #17
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Some of us know about it.

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Old 11-12-2019, 09:32 PM   #18
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Nice. I should have known you guys had that covered.
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Old 11-16-2019, 09:15 PM   #19
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Quote:
Originally Posted by hiperfauto View Post
Some of us know about it.

Neat! Is that any better than buying two 45 DCOEs though?
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Old 11-17-2019, 06:24 AM   #20
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Quote:
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Neat! Is that any better than buying two 45 DCOEs though?
nothing better in carbs than DCOE carbs
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Old 11-17-2019, 09:49 PM   #21
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Even with me bringnig up the progressive carbs. twin side drafts are the most pleasing to the ear and to the throttle response, never mind power.
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Old 11-18-2019, 07:57 PM   #22
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Don't forget pleasing to the eyes as well

https://www.youtube.com/watch?v=btL9mVxaVIg


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Old 11-20-2019, 12:36 PM   #23
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Alright....probably a stupid question, but can DCOEs be made functional as blow-through units?
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Old 11-20-2019, 12:38 PM   #24
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Quote:
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Alright....probably a stupid question, but can DCOEs be made functional as blow-through units?
Not stupid and yes, search turbo aircooled beetle by CB Performance.
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Old 11-20-2019, 12:56 PM   #25
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The bowl vent/static air port is on the inlet face - so it makes it pretty easy to do. For really high boost levels you might want to replace the bowl covers, I think. There were some factory turbo DCOE cars, I think, with reinforced covers.
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