Zenith Model B Carb

34Pietenpol

34Pietenpol

Member
I have a Model B Zenith carb for overhaul. When I took it apart there was no secondary well, just the jet stuck in the threaded secondary hole. I ordered the well and jet with the rest of the rebuild parts. The brass secondary well I received is correct but the threaded case hole does not match the well threads. Studying the hole, it appears I can drill and tap the undersized hole to match the secondary well's threads. Anyone with advice or an explanation for the undersized well hole? Thanks.
 
Something doesn't add up. Are you sure you ordered parts for a B carb, not an "A"? The B doesn't have a brass secondary well insert. It would help if you could post a picture of your problem area.
 
Agree with Sparky. Unless I am mistaken, the hole you refer to "with jet stuck in it" is the hole for the Idel Jet. And possibly the Idle Jet is installed in it. Yes, pictures.
 
Both of you are correct. This is the earlier version of the B Carb using the round float and with the bowl shelf as shown. It was reportedly an older overhaul, then left sitting on a shelf for years. I never ran it, decided it needed a thorough going over since I did not trust its history. Found the cap jet needle broken off and the main jet head snapped off in its boss as well as the idle needle issue we are discussing here. It appears that I have a Model A idle jet simply dropped into the secondary well hole. To me that means the Model B idle jet must have had threads on the needle which screw into the tapped threads inside machined hole in the casting. That would indicate no brass secondary well required. That makes sense to me, though I have not seen a true Model B idle jet needle. The third photo here has the threaded hole, the center one of the three in the bridge area, showing what I now suspect a correct Model B idle jet would screw into.

The idle jet I removed from this hole had no threads to screw into the tapped hole shown. Anyone have a photo of a correct Model B idle jet? The illustrations I have are of little help.

Thanks for the support! Bob C
 
Second try at photo upload.
 

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Correct, the B idle jet is threaded. Take a look here, the idle jet is on the bottom of the picture:
http://www.fordgarage.com/pages/jetflowrates.htm

It looks like your power jet tube is missing also. You can't buy them, but a piece of 1/8" diameter brass tubing can be substituted with a bit of modification to the upper casting. I replaced one just last week.

I can post some pictures of my B carb later today.
 
"To me that means the Model B idle jet must have had threads on the needle which screw into the tapped threads inside machined hole in the casting."
Correct

" That would indicate no brass secondary well required."
Correct.

" The third photo here has the threaded hole, the center one of the three in the bridge area, showing what I now suspect a correct Model B idle jet would screw into."
Correct.
As Bob C says. Go to Vince's site. You will find everything you want to know about B Carbs.
 
If you need a power tube, contact Vince. He sells them and they are a exact fit.
Installed 3 of them recently.
 
There is a power jet tube. There is no idle jet. These B Carbs have seen excellent service in Pietenpol Model A installations. The fuel tank is in the wing which provides great head pressure to fill the bowl.

Talked this over with my partner in this restoration. We are going to send the carb to the best shop we can. Any suggestions for a shop which does high quality B Carb overhauls?
 
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