Zenith Rebuilding
 

Disassembling the neglected, rusty, frozen zenith core can be a chore.
I should take this on as a video project, and probably will.
Heat is my new friend, assisting in splitting the core. The Venturi does release this way. My next issue is removing the secondary well. Drilling out with a reverse twist drill is my go-to final technique.
Any other ways come to mind?

Re: Zenith Rebuilding
 

Read tom endy's rebuilding article.
Looks like he covered it.

Re: Zenith Rebuilding
 

Bob - I recently renovated six Zeniths (three of them incredibly rusty), and three of them had stuck secondary wells. One of them I was able to flood with Kroil and then apply heat with my oxy/acetylene torch to the housing, and it freed up the secondary well. Didn't work on the other two. I tried easy-out on those two but no joy. So I had to drill out the wells.

In drilling I bolted the the body on my mill bed (a drill press will work fine) based on the flat of the body bolt, then supported the body with wedges. I centered the drill on the secondary well opening then tried the left-hand drill trick with no success either one. I ended up drilling out the brass secondary wells with gradually increasing drill sizes until the iron threads were just visible through the brass. I ran a tap down from there which forced the remaining pieces of brass down, and then I picked out the brass pieces. Chase the threads again, cleanup, lots of air, run a wire through the air channel, good as new. Oh yeah, lots of Evaporust to get things really clean.

In general I've had good experience removing stuck bolts using left-hand drills, heat and Kroil, but not in this case. I suspect the brass of the well is just too soft to engage the drill over the resistance of the threads.

Good luck.

JayJay

Re: Zenith Rebuilding
 

I would avoid drilling it out as you can easily damage the threads. I have removed many with an easy technique. Take a torch and heat the area around the secondary well until it glows red, then drop it in a bucket of cold water. It will then easily unscrew.

Tom Endy

Re: Zenith Rebuilding
 

Several times I have had stuck secondary wells that put up a fight.
Not pretty when they stick.
I will try the heat and shock in water.
If the casting has a hairline crack there isn't any good time to find that out.
Thanks for the knowledge and experience.
I am up to 45-50 and some are damaged when I get them cleaned up and apart.
Matching tops and bottoms has been the time consuming operation. The Restorer series by Schmauch clarified that process.

Re: Zenith Rebuilding
 

Guys, I have a fine point question regarding the reassembly of the Zenith. The secondary well in mine screws in until there are two or three threads showing above the brass well. I believe it is bottoming on the casting. Is this correct?

Re: Zenith Rebuilding
 

And the threads are sort of loose too. Is this correct also?

Re: Zenith Rebuilding
 

Look in tom endy's restoration tips.
http://www.santaanitaas.org/wp-conte...etor-11-07.pdf
There were three different secondary wells, I believe, only the third style is available.
The well gets screwed in and typically several threads of the casting are exposed when it is properly installed.
However, the well can block the comp jet channel. I modify the well with a file to correct this problem.
I think Endy covers this.

Re: Zenith Rebuilding
 

Thanks, Tom, I'll try that technique next time I have the opportunity. Thermal shock is a good technique to have in your bag of tricks for loosening stuck "things". I agree, drilling out is not to be undertaken without a thorough understanding of what you're doing, plus a good stable machine tool setup. I didn't put in my description that I also verified x- and y- flat, to assure perpendicularity of the drill to the casting, before I began drilling. Your way is quite a bit simpler.

JayJay

Re: Zenith Rebuilding
 

My drill out procedure is a little crude, but usually successful.
Heat is my new friend.

Re: Zenith Rebuilding
 

I use heat and have never had to drill out a secondary well.
I heat all around the well until bright red then I let it air cool until the red goes away then I put water on it. The wells will come out very easy without any damage to the screwdriver slot or the well and can be reused after cleaning.
If it does not come out easy after heating do not keep trying and tear up the screwdriver slot. You did not get it hot enough, heat it again and get it hotter than before. A propane torch will not work, you will need a oxygen - acetylene torch with a medium size tip. This method works on all stuck carburetor parts.

Re: Zenith Rebuilding
 

Oh my Gosh, thank you, thank you, thank you. I have purchased and read other's bookes. I have read an abbreviated version of this and done all that was in it. The other day, I found that the cap jet was leaking at its base. I carefully tightened it and tested it on the bench as stated. But today, I gave it another digital exam and the d!@#$ thing was wet again. I'll order gaskets from Brattons. If I go tighter I might strip something. For a rookie, "How tight is tight?" is an important piece of knowledge.



The black gasket that was on my main jet was much thicker than the red ones. Won't this lower my main jet orifice????


The other fine-point piece of knowledge is the tiny hole in the intake at the bottom. I have not noticed this hole, but I have been a victim of exactly what Tom describes. But due to experience, I have not over tightened the drain plug!

Re: Zenith Rebuilding
 

Are you using OEM jets? Reproductions of the main jet, and the cap jet can be the wrong length.

Re: Zenith Rebuilding
 

Bob, I'm in the process of restoring about a dozen zenith carburetors and was wondering about how to match up the tops and bottoms correctly. I searched but couldn't find that article by Schmauch. I checked the MAFCA "how to restore the Model 'A'" Technical article index but no luck. Any clues where I might find that publication?

It is so much fun rebuilding these old Zenith Carburetors. Built a jet flow tester, a float gauge, and made an electrolysis vat to remove rust (worked great too). Figuring out how to gently take apart frozen carburetors is quite the challenge.

Re: Zenith Rebuilding
 

The Restorer, March-April 2017,is first article, then consecutive issues, thru
November-December, 2017.
I believe MAFCA will copy the articles if you cannot locate the issues.
I made up a reference ring binder. Very comprehensive. Beautiful piece of work, the technical articles that is.
You will learn a lot getting into the task at hand.
Pm me with issues, I'm the first to say that I don't know, but maybe I do.

Re: Zenith Rebuilding
 

The judging. Standards have all the Zenith carburetors and details listed ,

Re: Zenith Rebuilding
 

The articles are better in my opinion.

Re: Zenith Rebuilding
 

Thanks Bob !

Re: Zenith Rebuilding
 

1930 coupe: your use of heat on the secondary well did the trick. Even used a propane torch to maybe a Very light orange tinge.
This was a very rusty bottom casting I soaked in derusting for several days.
Thanks.

Re: Zenith Rebuilding
 

Suggest get Paul Moller's orange cover book on rebuilding Model A carbs.