Location of exhaust crossover for choke

[ArmandsBronco]

My '73 302 has a 2 bbl motorcraft with an auto choke on it that requires hot air supply and clean air supply from an "exhaust crossover" that should be on the motor somewhere but I cannot locate it. I' even wondering if this was a replacement carb not original. Anyone have any ideas?

here is a pic of mine and a link Steve provided that explains:

http://s6.postimg.org/62g8u3gwh/73_Bronco_hose_openings_from_carb_parts.jpg

http://www.ford-trucks.com/forums/806018-choke-questions-answered.html

 

[admin]

The hot air tube and the fresh air tube both go down and press in to holes on your passenger exhaust manifold. That's the "exhaust crossover".

I've been messing with the same thing. I'll post pics later today if no one beats me too it.

Sent from my SGH-T989 using Tapatalk 4

 

[ArmandsBronco]

That would be great. I've got this apart this week end and the only thing I see is the very rear of passenger side exhaust where it looks like a threaded hollow tube rusted off (see pic) but it does not pass through into exhaust. I stuck a pin into the threaded tube and it butts up into steel.

http://s6.postimg.org/8fu1qqmvl/Exhaust_passenger_side_tap_for_stove_mix.jpg

 

[ArmandsBronco]

PS When changing out water temp sender on top of head, do I teflon tape it or no?

 

[904Bronco]

That would be great. I've got this apart this week end and the only thing I see is the very rear of passenger side exhaust where it looks like a threaded hollow tube rusted off (see pic) but it does not pass through into exhaust. I stuck a pin into the threaded tube and it butts up into steel.

http://s6.postimg.org/8fu1qqmvl/Exhaust_passenger_side_tap_for_stove_mix.jpg

Check the bottom of that bump out on the exhaust manifold for an outlet... Vacuum from the carb, goes through the body of the choke, out that threaded fitting, through some metal tubing (which appears to be missing), into the exhaust manifold (does not mix with the exhaust gases). Another metal tube come back up and then it pulls air into it from a hose that connects to that port on the carb. Kind of a conveluted system in a way, but it was standard back in the day.

You might have to make something up to replace it...

 

[admin]

That would be great. I've got this apart this week end and the only thing I see is the very rear of passenger side exhaust where it looks like a threaded hollow tube rusted off (see pic)

Bingo. You found it. And yes, that looks like the tip of your old tube is still stuck in there, just like mine.

There should also be another hole lower down on that same "bump out" on the manifold. See pic below.

The hole at the top is where hot air tube connects. The hole at the bottom is where the clean air gets sucked in.

The hole does not pass through into the exhaust. You don't want dirty exhaust air gumming up your choke. The "bump out" is simply an air passage that's cast into the manifold. The passage connects top and bottom holes, but doesn't open up into the exhaust chamber itself. It just absorbs the heat from the manifold and draws that air up to tell the choke when to open up after you've reached operating temperature.

I believe the reason you can't stick something clean through it is there's a filter inserted into that passage.

 

[admin]

Here's the choke tube kit I got, but haven't installed yet. I think I need to pull the manifold in order to get the old broken off tips out of the holes.

I'm sure some of our Bronco vendors carry them. I got this one from West Coast Classic Cougars because I was getting some other Mustang parts at the same time. :-X Sorry vendors!

 

[ArmandsBronco]

Thanks everyone!!! You are all awesome!!! Okay, well here is what I have so far (thank you Alpacket for the awesome pics that said it all and ADMIN who gave me the answer as I was crawling under the rig for a pic...HA!):

So the original system has a little unit that inserts from the bottom side of the exhaust manifold and threads through the top side of the manifold, with the hollow tube with exterior threads making its way through the threaded opening on the top side of the exhaust manifold.

The bottom side (clean air in?) has a ROUND head (can't take out with socket) with a single flat cut side of the head with a hole for the metal tubing to insert (not threaded). The top side has exterior threads and that is where the hot air return heads to the choke.

Have I got that right?

So the old unit top side is broken off and rusted tight :

http://postimg.org/image/d1q5z38el/

and lord knows how to try and get it unscrewed (never minding the rusted top side) from the bottom when the "bolt" unit head is ROUND:

http://s6.postimg.org/j3xspkwup/Bott...haust_unit.jpg

I SERIOUSLY DOUBT anyone sells the ONLY tool made to remove the unit from the exhaust (round with one flat side; like a "C").

I want this restored to 100% stock condition. No switching over to electric choke.

Can I find a new unit insert and get this repaired at machine shop, removing the manifold - since I'm going to remove it sooner or later anyway.

 

[ArmandsBronco]

It seems we are in the same boat on this one. Thanks for the tip on the kit supplier. It seems its time to pull the manifold and send to machine shop for making pretty and removing impediment.

 

[Steve83]

 

[ArmandsBronco]

thnx guru - that helps out a lot