Have an Ford Autolite 4100 carb here, in good condition except the air cleaner hold down stud is missing. Looking into the recess, it appears the threads are stripped out? The recess hole appears to be about 3/8" in diameter, although the upper hold down needs to be about 1/4" dia. Was it threaded originally? Can anybody shed light on this? .  Thanks.


Paul

mine is 3/8 unc at the carb end and 1/4 unc at the top end.
 
I needed a much longer one to accommodate a taller filter so I drilled the top of a 3/8 unc bolt then cut the head off a long 1/4 unc bolt pushed the two together and brazed them. I am useless at starting a die square hence the long bolt instead of a piece of 1/4 rod.
stuey 

Carburetor or top off....don't ant anything going down into engine.  If there is room you could double nut a piece of "all thread".....one nut under and one nut on top....red lock tite.  You can spent $20 and buy a 1/4" HeliCoil  kit.  No need to drill...just run the tap in the stripped thread hole and run in the new SS thread......break off the tang and you're good to go.  Still probably need a length of "all-thead."....and, I'd still Locktite it.  That is assuming that the original threaded hole was 1/4".

As Stuey points out, the original stud was likely stepped from 3/8"N.C down to 1/4"N.C.  I could make one like he did, although the base will need to be Heli coiled or epoxied in, due to stripped threads. Quite some time back, I enquired about a Helicoil kit & I think it was $36+ then, likely at least $40.00 now.. Thanks anyway for the information.  


Paul

Okay, I'll go with another cheap fix, maybe.  eBay for a 3/8" HeliCoil, fix the carb top.  Drill out the hole in the filter lid to 3/8"....nut, acorn or wing-nut..  Again with the "all-thread."   I sort of like all-thread for easy fixes........local 'nut and bolt' store stocks most sizes, course and fine, even in 4140 grade.

There are no threads in the carb top, it's a through hole, the threads are in the body. The original stud had a nut that helps clamp the top to the body.. If the threads are bad in the body the top will have to be removed to make any repair.

O.K. Jim, I'll take the top off & check it out..Thanks


Paul

Paul,

The main reason that the bowl threads get stripped out is that people think its a 1/4-28 thread.  ITS NOT!  Its a 1/4-24.  The  bowl is made of weak metal which I call pot metal that strips easily.  Doubt if there is enough meat there to allow a helicoil but good luck.  Chances are you will have to replace the bowl.  If you do, make sure you use a 1/4-24 stud.

Bill A

O.K. as 57 R Jim advised, the threads start in the lower body, not in the top casting hole. The threads are apparently 5/16" N.C. As far as I know this Autolite carb is off a 1965 Mustang. If I bottom the stud's thread in the hole the stud will need to be approx 4-3/4" long to reach the top of my air cleaner, (which I believe is an original 1957 unit) & include thread for the wing nut, which is also 5/16" thread.  So, at least I now know what I'm dealing with.. Thanks 


Paul