Firewall Empty Space

[ODZKing]

73 400hp with A/C.  What is the hole for?  Mine came with the plug which I have also seen on other cars.

[chargd72]

My '72 doesn't have that.  Washer hose?

[Dino]

Bob, I found this online, looks like there's a hose going through.

http://carphotos.cardomain.com/ride_images/3/183/2641/25456320013_large.jpg

[Dino]

Another one

http://carphotos.cardomain.com/ride_images/3/183/2641/25456320240_large.jpg

[ODZKing]

Huh, the mystery continues. Now, what is that line for?

[John_Kunkel]

That hole is where the controller for the NOX system mounts, it senses air temperature in the cowl and adjusts the spark timing according to air temp and road speed.

[ralley72]

Here is a picture,(its a little small in this picture) what that part looks like installed.

Mike

[ODZKing]

Interesting John.  I thought the OSAC valve (Orafice Spark Advance Control) did that.
That is the (square hole) on the firewall next to the round hole.
Also in the TSB 25-04-73D it mentions only the OSAC.  
http://www.hamtramck-historical.com/images/TSBs/1973/25-04-73D%20p1.jpg
http://www.hamtramck-historical.com/images/TSBs/1973/25-04-73D%20p2.jpg
I did all the reading that I could find to at least make it look like this stuff was hooked up properly.
Not saying I didn't miss something, that is certanly possible.  That's why I'm asking.
Is that a pre 73 item and they just left the hole? The plate that is over it is definately not home made.
Over the last 3 years I have collected probably 100 engine bay pictures or 3rd gens, and I see in 74 they mounted the bypass switch there.
Other years, some have a hole some don't!!  

[ralley72]

Part number 3656660 On the part it reads Control Valve. I pulled this on my 73 Satellite, 318 with A/C. I can post a picture of the part off the car.

Mike

[Dino]

I just found this:
http://www.hiltopautoparts.com/product/nos-mopar-1973-egr-switch-most-models/

And it mentions this:
EGR Switch:

This is the EGR switch [Exhaust Gas Recirculation] vacuum control switch for all of the listed models EXCEPT those with 340 ci 4 barrel & 400 ci 4 barrel engines. Fits models UP TO build date of March 15th, 1973. New old stock Chrysler part in original packaging.

[ODZKing]

Ah, 400 4bbl - on mine is on the radiator. See http://www.hamtramck-historical.com/images/TSBs/1973/25-05-73D%20p2.jpg
In fact I just took it off as I didn't want the hoses running across the fan area.