Cap and Comp Jet Helicoil repair
 

Both of these are 5mm 75 pitch threads. Checked local auto parts and no luck there. Trying to repair Zenith 3 bottom that I found in a box at an antique store. All I can find is M5 .08.

Re: Cap and Comp Jet Helicoil repair
 

Call Berts.. Brattons has it listed in its parts book..

Re: Cap and Comp Jet Helicoil repair
 

Can you find a SAE 10-34. It is only .00012 less in pitch and .007 smaller in diameter.

Re: Cap and Comp Jet Helicoil repair
 

Go online found some on Amazon years ago .local club members

Re: Cap and Comp Jet Helicoil repair
 

No such luck spent all afternoon searching.

Re: Cap and Comp Jet Helicoil repair
 

Are you sure it is 5mm X 0.75 pitch? That is an odd thread. Metric coarse is 5 X 0.8 mm and metric fine is 5 X 0.5mm. A pitch of 0.75mm is very close to 34 tpi, again odd!

Re: Cap and Comp Jet Helicoil repair
 

Try McMaster Carr

Re: Cap and Comp Jet Helicoil repair
 

Braze them closed then drill and tap to the proper size. Be very careful that you get them straight.

Re: Cap and Comp Jet Helicoil repair
 

Yes Zenith French Made!

Re: Cap and Comp Jet Helicoil repair
 

Sent email may be able to help you out,

Re: Cap and Comp Jet Helicoil repair
 

https://www.snydersantiqueauto.com/P.../gaskets-parts


https://en.wikipedia.org/wiki/Zenith_Carburetor_Company
They are an American Co. The 2 jet design used was developed by the guy in the above posting and with more research would probable find that the two jet design was used under license, payed to the designer in France, so used some metric parts. The carburetors were made in the United States not France and used the same parts that Holley and Ford used in their carburetors.

Re: Cap and Comp Jet Helicoil repair
 

Hmmm, Made in France - strange threads! I wonder what threads I will find in a Japanese copy I have. I'd like to get it going and I've asked before if anybody know of them and did Zenith parts fit. I received no responses so I guess I'm on my own. It looks to my (non expert) eye that it was a double venturi type. Do they even make the uniquely double venturi parts for those now?
BTW, it is branded KTK.

Re: Cap and Comp Jet Helicoil repair
 

Snyder's has the '28 twin venturi but it is any bodies guess if it fits your carb. Only you will know for sure when you buy one. :p

Re: Cap and Comp Jet Helicoil repair
 

The one from Brattons fits and works just fine.. I think its the same one Snyders sells..

Re: Cap and Comp Jet Helicoil repair
 

I use the tap all the time to chase threads I have used it for years. The challenge is the threads are worn away and even cleaning up what's there isn't enough to hold the jets.
All I can find is a 5mm .08 helicoil and not .75.

Re: Cap and Comp Jet Helicoil repair
 

What about making some thin wall inserts using US thread but drilled and tapped for the 5m.75 thread.

Re: Cap and Comp Jet Helicoil repair
 

Finally heard back for Steve at Bert's at as I was afraid they did not have a resource for the 5mm .75 helicoil for the repair. Because there is no way access the passage for the secondary well you cannot simply fill and retap. I had another old Zenith bottom that I tested using a 5mm .8 helicoil and it worked. It holds the jet and seals with no leak. Tends to chew up the threads a bit on the jet but is much better solution than JB Weld.

Re: Cap and Comp Jet Helicoil repair
 

The secondary well is a different size then the 5M.75 jets. So you need more then just the jets thread repaired to refurb this carb?

Re: Cap and Comp Jet Helicoil repair
 

The secondary well threads are not relevant here. Only the passage to the comp jet which cannot be reached if one was to fill the area with brass and cut new 5 mm threads.

Re: Cap and Comp Jet Helicoil repair
 

Take the jets to a plating shop and have a copper or nickel flash put on the fittings. This will easily add .0002" to the surface of the threads. Make sure you put wax in the orifice of the fitting otherwise it will get plugged.

Re: Cap and Comp Jet Helicoil repair
 

That was my next thought.

Re: Cap and Comp Jet Helicoil repair
 

If the goal is a good fitting jet, i would tin the threads of the jet carefully with 50/50 solder.
Just don't tighten it too much.

Re: Cap and Comp Jet Helicoil repair
 

The Challenge was the threads in the bowl were all but gone.

Re: Cap and Comp Jet Helicoil repair
 

I read that 3 times and still miss read it. Sorry about that. Even if you were to install a hel-coil you would still need to drill/tap oversize to install. What about soldering it in place? About the only time it would need to come out again would be full rebuilt.

Re: Cap and Comp Jet Helicoil repair
 

I suggested tinning the jet threads, because I can't imagine getting in there to repair what is left. You wouldn't need much for threads to hold the jet if it's tinned.

Re: Cap and Comp Jet Helicoil repair
 

Ok, Try Brattons, Its in his parts book.. Just as you want..

Re: Cap and Comp Jet Helicoil repair
 

Where is it listed? I looked on line and didn't see any Heli-coils listed only the tap under carburetors. Or is it just in the printed catalog? Do you have a parts number? We too have a couple of bottoms that could use some work, but not as rare as a Z3 so have not been in any rush to fix.

Thanks

Re: Cap and Comp Jet Helicoil repair
 

Did not notice he wanted a Heli-Coil, Thought he wanted a Tap..

Re: Cap and Comp Jet Helicoil repair
 

Bummer, would have been easier fix then some of the suggestions so far.

Re my suggestion about soldering it in; if that jet is screwed in without the gasket it can interfere with the well going all the way down. So a spacer under it might be needed.