Continuing Carb Frustration

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lsquaredb

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Hi Everyone,

I've been having lots of problems with my rebuilt Zeniths: bad idle solenoids, bad needle valves in rebuild kit, a bad float. Now my mechanic tells me one of the carbs needs to be replaced because the idle circuit is blocked and they haven't been able to unblock it.

I'm wondering should I try to find another Zenith or get some new Webers? There seems to be a difference of opinion on which works better. Something that worries me are reports that the 32/36 DGAV are too tall with the stock air cleaner and interfere with the hood. How serious is that problem? My hood fits perfectly after a lot of work by the guys that restored the body, and I don't want to mess that up.

I was hoping to bring the car to Saratoga Springs, and now that's starting to look iffy.

Leonard

'70 2800CSA Bristol
 
Webers will cause air cleaner to sit higher and closer to firewall, may interfere with hood light too. I like the Zeniths in the 2800, strange that the idle circuit can't be unblocked. A used one should be under $100, make sure it is same vintage.
 
you're going to have to decide whether a used Zenith, 45 years old and needing to be gone through and "made the same" as the one you have, is a better option than a pair of new or used Weber 32/36s which will need less attention. Depends too on your satisfaction/trust level with your carb guy.
 
HB Chris said:
Webers will cause air cleaner to sit higher and closer to firewall, may interfere with hood light too.
Click to expand...

I have 32/36s on my 2800CS and use JAM adapters to mount the stock air cleaner. As Chris notes, the air cleaner does sit farther back, causing it to interfere with the lens on the hood light. I'm not sure that it also sits higher, but it might. If so, it isn't enough to interfere with the hood or crush the sound insulation. In other words, the "closer to the firewall" is a slight problem, the "higher" isn't.

Having said that, my car runs great with the 32/36s. My Webers have manual chokes, so there are no coolant or electrical connections to deal with.
 
An unblockable idle circuit sounds strange, can he show you the blocked one vs the good one so you can see yourself?

lsquaredb said:
I've been having lots of problems with my rebuilt Zeniths: bad idle solenoids, bad needle valves in rebuild kit, a bad float. Now my mechanic tells me one of the carbs needs to be replaced because the idle circuit is blocked and they haven't been able to unblock it.
Click to expand...
 
Stevehose said:
An unblockable idle circuit sounds strange, can he show you the blocked one vs the good one so you can see yourself?
Click to expand...
I agree, all this is fixable....if you want to. Just takes the time it takes. I run a pair of Weber 32/36, with K&N air filters. infinitely adjustable. Used in thousands if not millions. You can become an expert in tuning and achieving synchrony! But I do not incorporate the original air filter. So perhaps this is an aesthetic limitation. Install the Webers and drive to Saratoga and regale listeners with tales of your new love of the WEBER!
 
Please note that the base section gasket if over/ under tightened, misaligned, etc, will cause your symptom. It is the vacuum source for the idle circuit that pulls the fuel.

Idle valves are snug. Do not over tighten. This will cut off flow.

It won't matter what you do to the idle screw if the two previous mentioned items exist.



Search for DQ's zenith carb rebuild for videos.
+1 for Steve- never heard of an idle circuit stopped up.
upload_2017-6-27_18-36-13.png
 
I had webers with weber air cleaner and coolant choke and it worked perfect till I got side drafts. I still have my Webers, only six months old and tuned if you interested or want to switch
 
Thanks to all of you for your help. I'm going to visit the car in the morning and check the things 61porsche suggested, then decide if I want to Weberize the car. I don't have much faith in the guy that rebuilt the carbs. I wish I had tried it myself. Years ago I had a 1946 Citroen with a Solex that I rebuilt. Parts were unobtanium, and I couldn't fit a newer carb because of manifold differences. I had to make the gaskets and accelerator pump diaphragm and seal up the throttle shaft with teflon plumber's tape. That was kind of fun.
 
do-not-swap-zeniths-swap-mechanic-STOP ;-)

IMHO, you wont be able to do this in a hurry, try to make rational decissions
if you have a good weber mechanic in your are and you can rely on their work it might make sense
 
I'm no Weber mechanic, but I did stay at a Holiday Inn Express just before I rebuilt my Webers 9 years ago. They remain as built and working well.
 
Get yourself a rebuild kit from classicgarage (the real thing, not the Walker stuff), get a box to rebuild the carb in (I do this so when crap goes flying, it stays in the box) and follow the overhaul instructions in the Tech Section on this site. I never rebuilt a carb in my life but did this for both of my Zeniths and they run really well. Alternative=Spanish interpreter and deQ videos.
 
I visited the car this morning. They showed me the gasket that had been taken out of the carb. It had two small vacuum holes rather than a larger single hole as in the picture above. Are there different versions of the gasket? Here is a picture from the kit from classic garage. It looks like it has two different gaskets.
classicgarage_2272_626418049.jpg
 
lsquaredb said:
They showed me the gasket that had been taken out of the carb. It had two small vacuum holes rather than a larger single hole as in the picture above. Are there different versions of the gasket?
Click to expand...

I'm no expert on Zenith carbs, so can't answer your question in detail. But I do know that including multiple, different gaskets in a set is pretty standard. To the manufacturer, the cost of the gaskets is low while the stocking and other supply chain costs are high. So if they include an assortment of gasket configurations, a single kit can service multiple variations of carburetors.

Is it possible that your mechanic used the wrong gasket? That is, if the kit included multiple gasket configurations to handle Zenith models A, B, and C, he grabbed the "B" gasket, but you have an "A" carburetor?
 
Yes, the kit has multiple gaskets that you will not need and there are such subtle differences between them that it is easy to use the wrong one.
 
Mike Goble said:
I'm no Weber mechanic, but I did stay at a Holiday Inn Express just before I rebuilt my Webers 9 years ago. They remain as built and working well.
Click to expand...

Senator, I served with a Weber mechanic, I knew a Weber mechanic, a Weber mechanic was a friend of mine. Senator, you are no Weber mechanic. (Prolonged shouts and applause)
 
Thanks Steve.

Yes, you can easily use the wrong gasket. The carbs were also used on Mercedes and Unimog and those set ups are different than what Zenith did for BMW.

If it were me and I had to get it going:

1. The original gasket- Phenolic had paper gaskets shellaced to either side. DQ- look the other way. Order the real BMW Mercedes gasket.

2. The four bottom section screws have to be torqued like a head gasket. Slow, steady, and incremental. Snug and a little more. 5-7 ft. lbs. Then do it again. This is important.

3. Find the air bleed jet on top. Stick your finger over it with the car running. If it's lean- meaning there's an air leak, this will tell you without taking the carb apart.

4. Work one carb at a time. I've never found both to have a problem unless it was a fuel issue.,

Zeniths have to be set up, linkage, and jetted. It's not plug and play. Steve- Amen? Even when you know what you're doing and you have the tools it takes time and parts and wise choices.

As we say in Texas-better to ride the horse you saddled. IMHO.

Kindest regards to all,

61
 
61porsche said:
Thanks Steve.

Yes, you can easily use the wrong gasket. The carbs were also used on Mercedes and Unimog and those set ups are different than what Zenith did for BMW.

If it were me and I had to get it going:

1. The original gasket- Phenolic had paper gaskets shellaced to either side. DQ- look the other way. Order the real BMW Mercedes gasket.

2. The four bottom section screws have to be torqued like a head gasket. Slow, steady, and incremental. Snug and a little more. 5-7 ft. lbs. Then do it again. This is important.

3. Find the air bleed jet on top. Stick your finger over it with the car running. If it's lean- meaning there's an air leak, this will tell you without taking the carb apart.

4. Work one carb at a time. I've never found both to have a problem unless it was a fuel issue.,

Zeniths have to be set up, linkage, and jetted. It's not plug and play. Steve- Amen? Even when you know what you're doing and you have the tools it takes time and parts and wise choices.

As we say in Texas-better to ride the horse you saddled. IMHO.

Kindest regards to all,

61
Click to expand...

amen, jerry ;-)
 
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