General Category > Quadrajet Carb Talk and Tips
7042238 What is it on the airhorn?
SUPRCHY:
Well after re-reading my previous post and looking long and hard at that cavity, I saw it. The standard HIC valve could fit there. So I ran down to the basement and grabbed the only HIC valve I have and sure enough - IT FITS!
Here is the proof sitting in my 7042238.
Suprchy
Cadman-iac:
Thanks for pointing that out. I'd seen the button on several tops, but never really gave it much thought. I would imagine that if you had a carb with this feature, you'd have to have that HIC valve in place or you'd have a good sized vacuum leak.
Just thinking about this, with it in this location, your "Bypass air" from it will only be going to the one side of the carb and manifold.
Possibly why it was moved to the center rear of the carb to evenly distribute the air? Just speculation on my part.
Rick
Kenth:
Rick, the idle bypass air is routed differently on these units with the HIC in that location.
Marked in blue circles.
Cadman-iac:
--- Quote from: Kenth on January 03, 2026, 03:07:25 AM ---Rick, the idle bypass air is routed differently on these units with the HIC in that location.
Marked in blue circles.
--- End quote ---
Interesting, I wasn't aware of that. Never would have guessed that's how they routed the idle by-pass air. I'll have to take another look at my early Cadillac carbs.
Thanks Kenth.
Cadman-iac:
I looked at a '72 Cadillac carb and it's got the same idle by-pass design in the air horn as yours does, but does not have the HIC valve in it, and the hole or passage is not drilled for it.
I'll have to look at one of the '69 Cadillac carbs I've got and see how the HIC passage was routed.
Thanks for pointing that out.
Rick
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