zenith carb replacments

mr bump

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Im wanting to replace the zeniths on my 72 3.0 cs with webber carbs. Which ones are the best replacement?
 

Stevehose

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I've had webers and zeniths and I would rebuild the zeniths. Better carbs when functioning properly imho
 

Ohmess

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My car came with dual Webers, but a buddy of mine with a background working on classic cars told me that the main reason Webers were recommended is because folks didn't want to take the time to learn about the Zeniths.
 

mr bump

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Zeniths are a great but complex carb, webbers are a easy carb to maintain. So it realy is a difficult decision to make.
 

Mike Goble

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I put some Weber DGV's on my daily driver Bavaria and they work very well. Webers are easier to work with than the Zeniths, parts are much more available and literature is more plentiful. The Zeniths have a vacuum operated secondary, and there is basically no adjustment of the opening point or rate. My Webers have mechanical secondaries, so it's easy to determine when they open and close.
 

MyFemurHurts

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My Coupe is running Weber 32/36's DGAV's, and aside from a little crankiness when dead cold, I like them.
 

jmackro

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My Coupe is running Weber 32/36's DGV's, and it runs great when dead cold, because the DGV's use a manual choke. Pull out the cable when cold, push it part way in after start, all the way in when warm. Crude but effective.

I never had much luck with the coolant-operated choke carbs.
 

mr bump

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I used 32/36 dgvs years ago in motorsport and they were a doddle to set up and get the jetting correct. I was thinking of going for 38 Dgas webbers to give it just that little more.
 

jmackro

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I was thinking of going for 38 Dgas webbers to give it just that little more.

What do you mean by "just that little more" ? Using carburetors that are too large for an engine's displacement results in airspeed through the venturis that is too low to properly atomize the fuel. Carb sizing is one of those situations where more is not necessarily better. Unless you are running a 3.5L engine, or only run at high rpms (e.g., racing), you'll probably be happier with 32/36's.
 

mr bump

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The car will be going on the rolling road when the new carbs are fitted, and when we were setting up the 32/36s for racing, we jetted it in a way where we could have done with a bigger carb but our rules said no carbs bigger than a 32/36 dgv/dgav, so 38dgas carbs have a lot more ajustment by way of fetteling and jetting to optimise power, And putting a car on a rolling road is the best way to set up carbs.
 

mr bump

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I do have 2 sers of triumph daytona motorbike carbs, so as soon as the manifolds are made and linkages worked out, they will be going on with a gas flowed head. Im quiet looking forward to seeing what they make on the rolling road and how responsive they are.
 

jmackro

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And putting a car on a rolling road is the best way to set up carbs.

I certainly agree with that.

My point about carb sizing had to do with how well the engine runs across its entire rev range. Sure, on an engine with head work, performance cams, headers, etc., big carbs will produce more power at the top of the rpm range. My point was that if you intend to drive that beast on the street, and want it to idle and transition smoothly through the mid-range, then overly-large carbs will not work very well.
 
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1e9kalkid

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Zenith carb replacements

I'm currently in the market for a set of weber carbs for my 1970 2800CS. I've been looking at both Redline's 32/36's DGAV's or their 38 DGAS, but on Redline's website the say that "All three digit K kits (32/36's DGAV's) are for racing and offroad use only and must never be used on the highways in California".

Can any of you Californian owners shed some light? It sounds as if a pair of 38 DGAS Webers are the manufacturers solution? Also, is electric or manual choke better? Any body want to weigh in?
 

Mike Goble

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I'm currently in the market for a set of weber carbs for my 1970 2800CS. I've been looking at both Redline's 32/36's DGAV's or their 38 DGAS, but on Redline's website the say that "All three digit K kits (32/36's DGAV's) are for racing and offroad use only and must never be used on the highways in California".

Can any of you Californian owners shed some light? It sounds as if a pair of 38 DGAS Webers are the manufacturers solution? Also, is electric or manual choke better? Any body want to weigh in?

I drive my Weber DGV carbed 72 BMW all over California with no problems. I bought a couple of used DGV's from a man who was returning his Datsun 240 to original, so there was a little adapting to do with the linkage and bracketry, but where there's a drill there's a way. I rebuilt them with the kits that came with them, and for the jetting configuration I turned to a Weber man from the 2002faq page, Creighton Demarest, aka c.d.eisel ( post #10 )

http://www.bmw2002faq.com/topic/102031-installed-the-synchronous-link-weber-3236/

The throttle response is smooth as butter throughout the range, from low idle to 6000 rpm. I didn't hook up the chokes and haven't had any cold starting problems at all. It's going to be 80° here in San Marcos today, so I'm living the good California life.
 

Peter Coomaraswamy

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Questions/comments: I have a pair of Webers that could probably use a rebuild that I would be happy to trade? for a pair of Zeniths if that is of any interest. The Webers ran pretty well and I put new ones on anyhow, but with a rebuild they could work great I think (I also have linkage pieces). And my question is can anyone recommend someone who can rebuild Zeniths? I'm in Texas and I'm sure some of these people exist, after all there is a whole series on Bigfoot and Megladon!

Thanks
 

Stevehose

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I've not used him but sure looks nice:

http://www.paltech1.com/


Questions/comments: I have a pair of Webers that could probably use a rebuild that I would be happy to trade? for a pair of Zeniths if that is of any interest. The Webers ran pretty well and I put new ones on anyhow, but with a rebuild they could work great I think (I also have linkage pieces). And my question is can anyone recommend someone who can rebuild Zeniths? I'm in Texas and I'm sure some of these people exist, after all there is a whole series on Bigfoot and Megladon!

Thanks
 

jmackro

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"All three digit K kits (32/36's DGAV's) are for racing and offroad use only and must never be used on the highways in California".

The only "8XXX" part #'s for BMW's that I see on the Redline website are for a 32/36 on a 2002. All other 4 and 6-cylinder kits have three digit codes, and as such are not CARB approved. The parts vendors' lawyers advise them to print that disclaimer, which basically says: "we're telling you to only use these carburetors offroad; if you get busted for using them on the street, don't say we didn't warn you".

In practice, since there is no emissions inspections here for pre-1976 vehicles, you can run whatever you want on an e9.

It sounds as if a pair of 38 DGAS Webers are the manufacturers solution?

Although your reading of the Redline website might imply that CARB is OK with 38/38's, I suspect that any deviation from the factory-supplied Zeniths is technically verboten. Given that no Weber is strictly legal on an e9, it is more important to match the carburetors' size with your engine's displacement. In general, 32/36 works best on 2800 and 3L engines, while 38/38 is more appropriate for 3.5's.

Also, is electric or manual choke better?

I already weighed in on my preference for manual chokes back in post #7. But I can appreciate that others might prefer water or electric.
 
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sreams

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My car came with dual Webers, but a buddy of mine with a background working on classic cars told me that the main reason Webers were recommended is because folks didn't want to take the time to learn about the Zeniths.

I think the opposite is also true. Many think the Webers aren't ideal because they haven't taken the time to learn them and get them right.

Most of the recommendations for jetting DGVs on an M30 I've seen suggest secondary main jets that are too rich as compared to my experience. I'm running 140 primary mains and 110 secondary mains on my otherwise stock M30B35, and along with the other jets (tuned with a wideband O2 sensor), I couldn't imagine a carbed car running much better than mine does. There are no dead spots. Power/torque are evenly progressive with pedal travel. I just had it on a Dynajet dyno, and the torque numbers were generally better than I've seen from stock 535i and 735i numbers using the fuel injected version of the motor. I'm seeing a 187 lbft peak at 3400rpm (lower RPM than the injected B35s), and between 174 and 185 lbft between 2100 and 5000 rpm at the wheels. This with the "lowly" DGVs.

I think the real issue is that people give up on both the Zeniths -and- the Webers before they ever get them tuned correctly.

-Scott
 
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