Zenith Carburetors

[Cape Codder]

My car is not running as well as I would hope. After checking the timing several times, gapped the points to .020" and set the gap on the plugs to .035" I have decided my problem is within the carburetor.

Having read Restoring the Model "A" Carburetor The "Rex" Reheis Way and also The Model A Ford Carburetors by Paul Moller I find myself confused. Not really knowing about the inners of the Zenith I have compared some of the numbers these two gentlemen provide.

Reheis Moller
Main #61 drill / .039" .035"
Cap #61 drill / .039" .036"
Compensator #63 drill / .037" .037"
Idle #75 drill / ,021 .021"

Both of these men give the dimensions for the Compensator and Idle Jets exactly the same, while the Main and Cap have different dimensions? First, why? Secondly does .003" to .004" affect the carb that much?

Lastly, one of my jets has too big of a hole. Does it matter what type of solder I use to fill the hole? Incidentally they are from Mac's if that makes any difference.

Also what is the preference of the board for a float valve. I see no less than three different ones in the catalogs.

Sorry for being so long winded but this is my first try to really rebuild it correctly.

Thanks for your interest to answer my questions.

[Mike V. Florida]

Originally Posted by Cape Codder

My car is not running as well as I would hope. After checking the timing several times, gapped the points to .020" and set the gap on the plugs to .035" I have decided my problem is within the carburetor.

Having read Restoring the Model "A" Carburetor The "Rex" Reheis Way and also The Model A Ford Carburetors by Paul Moller I find myself confused. Not really knowing about the inners of the Zenith I have compared some of the numbers these two gentlemen provide.

Reheis Moller
Main #61 drill / .039" .035"
Cap #61 drill / .039" .036"
Compensator #63 drill / .037" .037"
Idle #75 drill / ,021 .021"

Both of these men give the dimensions for the Compensator and Idle Jets exactly the same, while the Main and Cap have different dimensions? First, why? Secondly does .003" to .004" affect the carb that much? NO it does not.

Lastly, one of my jets has too big of a hole. Does it matter what type of solder I use to fill the hole? Incidentally they are from Mac's if that makes any difference.
This one is a little complicated. You see it is not just about the size of the hole but the shape as well. I have not seen reproduction jets in a while but they used to be shaped wrong. If you look at an original jet the end is concaved with eh hole in the bottom. The repro were rounded on top. As for type and how much solder, any and just enough to fill the hole. You do not want to fill the tube. There were pictures on the net with cross section of jets but I can't seem to find them now.[/COLOR]

Also what is the preference of the board for a float valve. I see no less than three different ones in the catalogs. Where are you seeing three different floats for the Zenith? I only see one and I've checked Mikes, Snyders, and Berts.

Sorry for being so long winded but this is my first try to really rebuild it correctly.

Thanks for your interest to answer my questions.

Buy original jets already flow tested is my advice.

[Gunmetal blue2]

You seem to like reading books so why don't you get the book from Mac's on rebuilding the Zenith carb.

[Gary WA]

Read all of Rex's book he explains why his are a little larger, both will work fine!

[160B]

Originally Posted by Mike V. Florida

This one is a little complicated. You see it is not just about the size of the hole but the shape as well. I have not seen reproduction jets in a while but they used to be shaped wrong. If you look at an original jet the end is concaved with eh hole in the bottom. The repro were rounded on top. As for type and how much solder, any and just enough to fill the hole. You do not want to fill the tube. There were pictures on the net with cross section of jets but I can't seem to find them now.[/

Here are photos of original jets and jets that have been soldered and re-drilled. The original "nozzle design shape” is lost when you solder, thus orifice diameter cannot provide consistent flow due to the change in the internal nozzle flow characteristics.

[Mike V. Florida]

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Thank's 160B!!

[johnbuckley]

"...]You see it is not just about the size of the hole but the shape as well. I have not seen reproduction jets in a while but they used to be shaped wrong. If you look at an original jet the end is concaved with the hole in the bottom. The repro were rounded on top."
Just for my two pennyworth, I have used both shapes and can detect no difference.
"As for type and how much solder, any and just enough to fill the hole. You do not want to fill the tube. There were pictures on the net with cross section of jets but I can't seem to find them now."
Hey I'm getting confused now- surely any soldering we do is going to change the external nozzle shape slightly and the internal bore of nozzle significantly... which would add weight to my belief that nozzle shape change is not very signficant in stock As. The best (only?) way to check the jets are OK is to test them for flow rate and check the stream is smooth when doing it.

[JOES31]

My recommendation would be to get flow tested jets from Renner's Corner. Another possibility is to use the jets from the rebuild kit that Snyder's sells. I have had good luck with them. If you decide to spend the money and spring for a rebuilt carb I would definitely get one from a supplier that tests them before shipping to you such as Bert's or Renner's.

Now if you decide to spend the money on a rebuilt you should think about the new Zenith 13922 carb. About the same price and you keep your old one. If you don't care about the look and it's not a points car then that is another good alternative.