7042238 What is it on the airhorn?

[SUPRCHY]

  Hi,

     I picked up a Cadillac 7042238 Qjet and it has a feature I've never seen before! On the top passenger side front is a spring loaded pin through the airhorn. It's similar to some Oldsmobile Hot Idle Compensator covers i have seen. It looks like a tiny fitted spring loaded pin, nothing else there. I've included a picture of the item. Anyone know its function?

Thanks,

Suprchy

[Kenth]

You push it to hold the hot idle compensator closed when adjusting idle mixture screws.

[SUPRCHY]

Kenth,

Thanks for the reply,

   Yes, I am familiar with the Hot Idle Compensator(HIC) "TEST" button and I only mentioned the HIC cover as a reference to what this pin looks like. However this is located on the top of the airhorn not the rear of the float bowl. My 7042238 does not use a HIC.
   Should I add more photos to better show where this is located?

I do appreciate your information,

Suprchy

[Cadman-iac]

  I've seen those on several of the old Cadillac carbs I've got as well.  I've always figured they were some sort of an early bowl vent, but never really gave it much thought.
  I'm sitting in my doctor's office right now, so can't look at one to see exactly what's underneath it, meaning, does it sit above the fuel in the bowl, or is it located over the idle by-pass passage, i just don't recall.
 Would be nice to know for sure what it's purpose is.

 Rick

[Kenth]

Kenth,

Thanks for the reply,

   Yes, I am familiar with the Hot Idle Compensator(HIC) "TEST" button and I only mentioned the HIC cover as a reference to what this pin looks like. However this is located on the top of the airhorn not the rear of the float bowl. My 7042238 does not use a HIC.
   Should I add more photos to better show where this is located?

I do appreciate your information,

Suprchy

The HIC in 1972 Cadillac 7042238 Qjets of this is located in the float bowl under the pin in air horn. You need to take off the air horn to see it.

[SUPRCHY]

   Kenth,

Ok, I apologize as I did not know that there were any other HIC configurations. I do have the airhorn removed and unfortunately there is just an empty cavity. I guess that someone removed whatever was there years ago.

   Would that be Part # 7035667?

Suprchy

[Kenth]

No reason to apologize, we all live and learn

Yes, that is the part-#.

[Cadman-iac]

  My carbs that have this are all disassembled, so I don't know what the system looked like either. Would you have a picture of one, or can direct us to an illustration of it somewhere?
 Thanks for the education. Learn something new everyday.

 Rick

[Cadman-iac]

  So that little nub sticking out of the plate on the rear of the early carbs is a test button for the hot idle compensator? Never knew that!.

[SUPRCHY]

To all,

Here are the Photos I have;

1.) 7042238 Airhorn Topside Pin is from the internet and shows the pin from a top down view.
2.) 7042238 Airhorn Underside Pin is from my 7042238 and shows the pin from underneath the airhorn.
3.) 7042238 Float Bowl Cavity is from my 7042238 and shows where the valve would be if it were there?

This is just my best guess so please jump in and correct me if I am wrong. I do not want to add to the misinformation that is already out there. I am just trying to figure this carburetor out.

Does this valve/compensator look like the ones that go into the rear cavity or are they different? I don't see how they could be the same if that is indeed where it fits on this carb.

Thanks for all the info,

Suprchy

[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]

Rick, the idle bypass air is routed differently on these units with the HIC in that location.
Marked in blue circles.

 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