What is the thread size of the where the bowl plug screws in?
The larger thread 9/16-24 is in the iron boss of the carb base for the drain plug assembly.
The little drain valve needle is 1/4-32.
What about the needle valve lock screw and the spray needle? We should have all the sizes here for reference.
Here you go:
Spray Needle Valve Lock Screw (top hex nut) and Gas Inlet Elbow are 1/8 NPT. (Pipe thrd.)
The Spray needle valve is 1/4-32
The Float needle valve seat threads are 1/4-32.
The Spray Nozzle is 3/8-24
The needle valve is 1/4 x 32, same as the float valve seat. The needle valve lock screw is 1/8 NPT (pipe thread), the same as the inlet.
I don't think I've seen a drain valve needle supplied by Ford or Holley that is 1/4 x 32, I believe they are 5/16 x 16 or 1/4 x 20.
Some of the reproduction drain valves do not work because they are not threaded deeply enough for the stop cock to screw far enough into the seat to shut off the drain passage.
Does any one know the thread size of the pack nut or, another way of asking for the same info: the size of the inlet elbow at the pack nut end?
Thanks in advance, Bill
Thanks, was wrong on that needle drain valve, 1/4-20 is what I have seen.
As for the pack nut Bill
the pack nut is 1/2-18
Got it, Dan. Thank you.
Can you edit the diagram and add these thread sizes to the diagram so that the information is all in one place?
Thanks for posting this information.
There are a lot of odd threads on carburetors. Almost every one has some odd threads. Most common of the odd ones (if that makes sense) is 24 tpi and 27 tpi. Also quite a few 32 tpi. But the pack nut on early Kingstons vary either 1/2 x 18 or 1/2 x 20. Some pack nuts are 1/2 x 24, some are 9/16 x 18, 20 or 24 tpi. Stromberg liked 24 tpi, Zenith 27 tpi and Schebler 27. Some of the carbs like U & J were built on metric specs so they have some metric threads and some Imperial Machine sized threads. I have about 50 different taps and probably a dozen non-standard dies. Most are made in China now, the old ones are hard to find and surprisingly enough, hard brass or Silicon bronze wears them out in a hurry. Even the better quality ones don't last long, especially if you are threading in the lathe. Oil helps.
OK That was fun, thanks Stan for the help. That needle valve drain plug is 3/8-20, checked several on hand. Thought 1/4-20 was too small
Here is the rev with thread sizes by the part descriptions, found in Word/Paint there is a text function....so this is better.
Dan, Thanks for adding the thread sizes to the diagram.