Single idle by-pass orifice

[F250 Restorer]

17059247: I was surprised to find that there is only one idle by-pass hole, measuring .125.

Is that normal?

Mix screws still oem plugged. I'll be doing cliff's first recipe on this. What is the best way to remove the plugs and slot the area around the screws for easy access?

[Kenth]

The hole is not idle bypass air, follow the hole to the float bowl reveals it leads to a full manifold vacuum source used on this unit.

[F250 Restorer]

So, the hole connects to the oem normal by-pass air passage, allowing air (vacuum) to by-pass the throttle plates, by-pass the venturi at idle. The engine is sucking air through the air horn, bypassing the venturi, and out the mentioned hole. And ... you're saying it is not an idle by-pass hole?

[Kenth]

Yes, the holes does NOT connect to the "normal" idle air bypass channel openings.
At least last time i checked....

FWIW

[F250 Restorer]

You are correct. I assumed it was by-pass b/c it is in the by-pass grove. But, after checking, if it were to be idle by-pass, it would have been bored in the other end of the grove. My bad. Thx.

I guess I am perplexed that a QJ for a 350 sb did not come oem with a bit of by-pass air.

PO had filled some of the v. ports with plaster of paris. Nice.

[Kenth]

There is some "idle bypass air" thru the hot air channel from choke to floatbowl on carbs with hot air choke. The restriction is about .092" in the choke housing tube seal.

[quadrajam]

About "plaster of paris" in the above post. Around here there is a mud wasp also
called dirt dobber that makes a single cell nest in small auto part holes. Looks just
like plaster of paris. That may be what your seeing.

They especially like 3/8 exhaust bolt holes and plugging up 3/8 hoses and tubing.
Aggravating.

[F250 Restorer]

There is some "idle bypass air" thru the hot air channel from choke to floatbowl on carbs with hot air choke. The restriction is about .092" in the choke housing tube seal.

Ah, mystery solved. Thanks for enlightening me. I think that Cliff had mentioned that in another post, but it didn't register until you mentioned it. Thanks.

Just for my own curiosity, if this is converted to e.choke, and the v. blocked, is it possible to drill the by-pass in the baseplate? When one of the by-pass slot already has a hole for vacuum in it?