I am rebuilding a Holly unrestricted bore carb that I picked up at a swap meet. What I am finding is there are no threads in the carb body for the spray needle to screw into---it relies only on the clamp nut to hold it in proper position. The clamp nut does have threads.
My other Holly carb, which is the restricted bore design, does have threads in the body of the carb for the spray needle to screw into and uses the clamp nut only to clamp it tight in position.
My question is am I missing a part for the unrestricted carb or was this a design change from one to the other?
That's probably the reason it was for sale at the swap meet.
Nope, no design change. Straight-through or swayback, it should be threaded. I hope you didn't pay a lot.
I have the 1/4 -#32 tap and can put threads in there for you. That is if nobody has drilled that passage oversize. Contact me offline .
Stan & Steve , ya you get what you pay for they say---but at $5.00 bucks not hurt too bad--maybe I can make it work.
Jack, thanks for your generous offer but after looking at it a little closer it has been drilled out. Can I maybe sleeve it? I have a tap. Joe
Maybe you can press in a bit of pipe of the right size and tap it.
Years ago I found one like that and I tapped the body then made a brass plug that I threaded into the body after boring it and tapping the plug for the needle valve. It probably was not worth the effort given the availability of decent cores but I have a thing about not scrapping anything that can be made useful and since I have way more time than money it kinda made sense to me!
I don't think there would be a Heli-coil that would work. I would put a tag on it to remind you what the problem is with it and put it in the back of your parts stash.
Well, I got the carb fixed and working. I used a model T level of repair to do it. What I mean by that is "work with what you've got cause your way out in the country and just got to get Ol lizzy to go!!"
I mentioned in my first entry that the clamp nut had some internal threads but they were only at the end that clamps the needle-- not the nut end. So what I did was to tighten the clamp nut a little at a time and turn the needle back and forth many times using a little light oil. This formed more and better threads in the clamp nut so I could now screw the
needle down just fine.
The next problem was I ran out of thread length on the needle before it would screw in far enough to reach the spray nozzle. So I chucked the needle up in my lathe and turned the shank dia. Above the threads to the minor dia which gave the needed clearance for full depth to reach the spray needle.
Put it in my 1915 and it started right up and runs fine. I all thke it for a test drive tomorrow if it stops raining here in Frankenmuth, Mi. Joe
Well done, congratulations!