Want to try something

[Frank400]

the first carb I built with one of Cliff's kit and parts and after reading his book was a 17059217 on a friend's 400 small block.  I am very pleased with the results, thanks to Cliff's parts and book.  Now I want to experiment something.  I'd like to relocate the upper idle air bleed to the air horn.  It currently is at .067 in the main body.  I'm planning to shut this bleed with epoxy and drill a hole in the air horn instead. 

     Should I go smaller than the actual .067 ?  I have to say the recipe is right on the money now, just want to try something new.  Same size but located in the airhorn what can I expect to happen ?

   Frank.

[ejowrench]

I think the only reason why it is recommended to relocate the idle bleed to the air horn because it is easier to resize an air horn bleed  then an air bleed in the main body.  If you do not need to resize the bleed, I wouldn't bother changing the location.

[77cruiser]

Drill & tap for a 6-32 brass set screw, then change to whatever you want or need.

[ejowrench]

77Cruiser, That is what I do. I clamp a drill motor into my vise with the chosen size drill. T

[Frank400]

do you guys hold the set screw in your hand while drilling ? 

[Cliff Ruggles]

The airhorn idle bleed would be a "direct" bleed, it needs to be about .015" smaller than one above the down channel doing the same thing.

I never relocate the upper idle bleeds, unless it is one of the Chevy carbs with the HUGE bleeds above the down channels, and then, in most cases we will tap it for 4-40 and put in a small brass set screw, then drill the airhorn for the idle bleeds instead.....Cliff

[ejowrench]

Get a drill with the desired drill bit and clamp the drill motor into a vise. Carefully hold the screw up to it and start drilling. My Millwakie  drill has a feature that holds the trigger down so you don't have to. When it's drilled deep enough, cut the screw to length. Thread a nut over it and put it in a vise. Now you can use a hack saw to cut a groove in it so you can screw  into a tapped air horn. After you cut a groove, take a screw driver and lightly tap it into the groove for a precise fit. Then 'upset' the head with a few light taps with a hammer to peen out the head so you can tighten it into the threaded air horn.  After all this, you will probably need to re-drill the hole again to size. Make sure both air bleeds are the same length. Also use red Loctite on threads.

I personally prefer to screw into the bottom of the airhorn so if the bleed screw should ever come loose and fall out, it will not be injested into your engine. However, you will have to remove air horn to replace when tuning.