T-Man700
Well-Known Member
Can someone tell me what this small item is on the right side firewall? My 72 must have had one because it has the 2 holes where this mystery item is in the photo.
Firewall mystery part on 72 Dart
- Thread starter T-Man700
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Anti noz valve or some name like that. Emissions crap
My 11/1971 built 340 Demon does not have one. But the dimples are there.
Dartswinger70
Well-Known Member
Ok this was funny I dont care who ya are...
T-Man700
Well-Known Member
My 72 Demon was built on 8/26/71, very early for 72’s.
T-Man700
Well-Known Member
Your car was built in 1970, in November?
CA car? All 73, all models had it.
cudamark
Well-Known Member
So, the first photo is not your car? If yours came with an OSAC valve it would have three holes there in the firewall. Two for the mounting screws, and one big one for the back side of the valve. Maybe something else was mounted there at one time.....electronic control module maybe? In '74 they decided to install the OSAC in the air cleaner housing.
73 OSAC hole. They actually go into the cowl plenum.
74 air cleaner
T-Man700
Well-Known Member
No, the car in picture is not my car. The photo was taken at the Mopar Nationals years ago. I just wondered what the holes were for on my firewall. I believe this car was a 72 as well.
T-Man700
Well-Known Member
Interesting
Vaanth
Well-Known Member
The device shown on the firewall is the orifice spark advance control (OSAC) valve. OSAC was first used in 1973 for California and federal applications.
As earlier noted and shown, the OSAC valve mounts over a square hole through which the OSAC thermal sensor fits. One hole on either side of the square hole is for self threading 1/4"-20 bolts. A 1972 vehicle would not have this type hole in the firewall from the factory.
If the 1972 holes in question are a bit further to the passenger side, and there are two self threading screw holes, vertically stacked, and a small round hole next to them as shown in the following image, it is the mounting point for the control unit part of the NOx (oxides of nitrogen) system which is part of the overall Cleaner Air System (CAS).
If the car was not equipped with this system, there will be three dimples, or partially punched holes, in place. The three dimples started appearing on cars in the latter part of 1970.
This particular NOx system was used on California cars in 1971-1972, and some federal applications in 1972. The control unit is shown in the following image:
The device in this case is for an automatic transmission car, and is the control unit part of the system. The thermal part of it senses temperature in the cowl plenum. The control unit triggers the solenoid vacuum valve based on temperature and vehicle speed.
The following image shows the system layout:
The following image shows the wiring diagram for the system:
For more information, see section 9A of the 1971 factory service manual, or section 25 of the 1972 factory service manual.
A previous owner hacked a hole in the firewall of my July 1970 built Duster for one of those things. One of a few abominations I have slowly been fixing.
T-Man700
Well-Known Member
Yes, I do have the three dimples on the firewall, I guess someone in the past put something there that didn’t belong. Thanks for your input and time.
Mine is missing the dimples now after I welded a flat plate in it!
ragtopfury
Well-Known Member
Josh's 73 Dart Sport had it, but now it does not.....
Ant
Well-Known Member
My 73 Dart has that OSAC valve, and of course I bypassed it. I too thought it was a 73 and up only thing, but was not exactly sure.
wth i'm calling the feds
ragtopfury
Well-Known Member
Cool. Lemme get their number for you... 867.5309. Ask for Jenny.
i guess they only listen in cali......
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