I have a '56 Holley 4000 that has stripped threads in the air cleaner stud hole. I would like to do a HeliCoil repair. Can someone tell me the thread size? It looks like a 6mm. Who knows for sure? Thanks, Mike

Mike: Doubt a 56 carb thread would be 6 mm. Anyway, if a Helicoil repair doesn't work out, or if the kit is too expensive. I found that to be the case when I inquired, re a carb repair. Try J.B. Weld. It worked for me on a carb...

Paul

Had the same problem, and tried Permatex thread repair kit (unsuccessfully...see: archive). Finally ended up tapping float cover for next largest size thread (no drilling needed) and rigging an oversized stud/wingnut. Working fine so far with 4 point-only mount.

6 VOLTS/POS. GRD. NW INDIANA

Thanks for the replies guys. I've found that it's 1/4-28. I'll try the HeliCoil and let you know. Mike

Fireball 56

I'm having the same issue, and I'm sure it's NOT 1/4 X28. I've tried matching it to my thread gauges and nothing that I have is the same. It must be metric.

Jim

Not metric threads on the lower part of the Teapot air cleaner stud.  The thread size is ¼ X 24.  Be forwarned that there is a small bronze bushing in the cover plate at the carb stud hole in the 4000 (Teapot) Holleys.  For this reason, it’s a good idea to remove the fuel bowl cover if working on the threads in the body as you don’t want to disturb that pressed in bushing.  If you look closely at the cover, there is a vacuum line that routes itself around the air cleaner stud and the bushing in the cover plate hole helps to keep the vacuum signal intact from one side of the air cleaner stud to the other.  For this reason, it’s always suggested to run the factory carb stud as the built in nut on it can provide some additional seal to the bushing as some of those bushings have been known to not be a perfect seal at that point.  If there is any semblance of a vacuum leak at the air cleaner stud around that bushing, then the power valve will remain open thus giving you a richer fuel mixture under both idle and cruise situations.

Lorena, Texas (South of Waco)

Ted:

You are exactly right about that bushing.  I have found them lacking in sealing, so I put a paper washer on top before I install the air cleaner stud, just to be sure.

John - "The Hoosier Hurricane"

I found a 1/4-24 thread repair kit on Ebay. They are made for Harley engine repair. Mike