Never measured one... You could go to your local hardware store and look for a slotted or Allen-headed set screw in fine pitch, re-drill and tap the hole for a bigger diameter....

 

It’s almost impossible to adjust these little screws without taking of the carb, which is pretty hopeless if you want to fine tune it. Maybe you can find a longer one so that you can access it with the carb in place. But maybe it would interfere with something, not sure.

 

It can be done, especially if you replace with an Allen head.

 

Take a bolt or screw with the same thread, pitch, cut it to links, put it in advice and use a dye grinder to cut a slot in it, smooth it out and see if that works

 

Cut to length sorry. Perhaps some all thread.

 

Ace hardware!

 

It’s almost impossible to adjust these little screws without taking of the carb, which is pretty hopeless if you want to fine tune it. Maybe you can find a longer one so that you can access it with the carb in place. But maybe it would interfere with something, not sure.

It can be done, especially if you replace with an Allen head.

This is on an old holley 750 I got for a steal. On my holley I actually inverted the set screw so the flat head is facing upwards. I then ground down a small Allen wrench to have a flat head and I use that to adjust my secondaries without having to remove the carb

 

Good idea. I'll try that next time I have it off.

I once looked into making the adjustment easier it but wasn't as simple as I initially thought and moved on to more urgent tasks....

 

Which has me thinking I could possibly make a custom bracket using pieces from a mechanical secondary shaft bracket that will allow secondary adjustment with a thumb screw while the car is running.

 

I don't know the size, but I replaced it with an allen head from the hardware store and would suggest that to anyone. It'll save you a LOT of frustration.

 

I’m fighting to get one out right now. I’ve tried heat (propane torch), PB Blaster, and just plain old force. Sucker won’t move…

 

Nitric Acid will dissolve the steel but not the aluminum/zinc alloy.

 

If you're still wondering, the secondary throttle adjustment screw thread size is 10-32. I used a 3/4" long hex bolt because for me, it's easier than the Allen set screw I had before. The slotted set screw that comes with the carb is flared slightly (hence the deep slot) to keep it from vibrating loose. Use a removable threadlocker or you'll lose the bolt.

 

Great! I had actually ordered some allen head 10-32 screws on amazon based off an ancient forum post somewhere. Glad to know they where right! Should confirm on monday when they arrive.

As for keeping my screw secure, 19 year old me decided that mucking up the threads with rtv to keep it from coming loose was the best course of action Its held for a few years and several adjustments so fingers crossed lol. The other carb receiving the fix will get a little dab of some loctite to be safe

 

Does that mean you’re only a few years older than 19? I thought you were an oldtimer like the rest of us! You sound so full of wisdom 😁

 

I just turned 24 this summer haha. I like to read a lot! And I love learning new things every day. I have the forum open on one of my 3 monitors and scroll through whenever I take a break from staring at and writing endless lines of C++ and C#

 

Just confirming that it is in fact a 10-32 size thread and the screws I ordered worked perfectly