Double Venturi Zenith

jgriffin

jgriffin

Member
I am cleaning out my carburetor and when putting it all back together it looks like the venturi needed to come out as it was stuck in the upper portion of the carburetor. Well I wasn't careful and it broke. It looks like the single venturi will work in its place, from what i can read. Do I need a different needle and seat or anything else? First timer here and I just don't want to have to order parts twice.
Thanks,
John
 
I wrote this waiting for the broken piece to cool so I could remove it. It doesn't look like I would need anything else. I will still look for replys but pretty sure I am good to go!
 
The idle jet should have #11,float bowl is different, main and cap jets are in a line from front to rear. If your DB venturi carbs was working good I would get a new venturi. Never tried to change to single venturi.
 
Gary WA said:
You can get a Db Venturi from suppliers! Berts has them
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All the places that I looked at are "out of stock".... including Bert's. �� But when first looking at Brattons they say the single will work so was thinking just going that route
 
jgriffin said:
All the places that I looked at are "out of stock".... including Bert's. �� But when first looking at Brattons they say the single will work so was thinking just going that route
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Try it may work, Done many carbs but never tried the single on double.
 
I have a single venturi on a carb that was originally for a double venturi and it works well. In fact I tried switching the venturis back and could detect no difference whatsoever. As I recall you may need to grind a small locating lug off the lower casting which was to stop the double venturi rotating. No need to need to change the jets. ( However contrarily you can't fit a double venturi in a "single venturi" lower casting as the cap jet will foul the inner venturi)
 
My venturi is broken and stuck in both halfs of the carburetor. For now I just left it since both haves fit tightly together. They are also surrounded by a gasket. Some of the suppliers have the double venturi available, it is just more expensive.
 
I've been watching this thread. I have a Japanese reproduction of the Zenith (KTK branded, I think). It was a double venturi carburettor and I thought I'd like to get it working well just as a curiosity piece. After what I have read, I will now source a single venturi and put it together that way.
You never know who you are helping by posting here.
 
I tried them both too, since my car is March 1928. The doubles give more bottom-end. You can feel it in the seat of your pants when you step on it. Just my opinion. I think Snyders may sell the doubles.
 
Gene F said:
I tried them both too, since my car is March 1928. The doubles give more bottom-end. You can feel it in the seat of your pants when you step on it. Just my opinion. I think Snyders may sell the doubles.
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So it looks like everyone is "out of stock" on the doubles. Since I am so new at this and haven't even driven mine yet I am going to stick with the single for now.


I am replacing it as we speak and have noticed a pin that is pressed in not allowing the venturi to slide done on the lower section of the carburetor. Seems as if I can just remove it and continue on. Any confirmation on that would be appreciated!
 
Here is a picture of the pin for reference
 

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The photo in post #14 looks like a jet from a Model B carb has been installed in the position where the cap jet is normally installed in the A carburetor.

Either that or someone has drilled the cap jet way oversized.

There is a B jet that is "upside down" compared to A Cap jet that has the metering port on the bottom that is below the threads. I do not have time to post a photo.
 
That is an early 1928 cap jet specific to the dual Venturi, the metering orifice is at the bottom of the jet.

The domed tip of the main jet is also early 1928, they soon found that capillary action was pulling fuel from the float bowl when the engine wasn't running. They added the dished / heavily chamfered tip to the main jet to eliminate this issue.
 
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A&L Parts are the only ones still making the dual Venturi and he has not unpacked all the tooling to make those since he changed locations a while back.
 
Dave,

Thanks for the correction.

I remember seeing the double venturis with the "skinny" cap and "skinny" main jets.
 
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