What's the official name and where can I find it? '74 Dart, 225 /6, A904 auto tranny. The vacuum switch on top of the snorkel and the heat riser tube from the exhaust to the bottom of the snorkel. Also, what connects where on the vacuum switch on the side of the breather? Getting ready to swap my Holley 1920 carb to the original 1945 model and want to hook everything up right. Thanks to all for helping me out!
Missing air cleaner parts and connections
- Thread starter sargentrs
- Start date
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pishta
I know I'm right....
The air cleaner part is the cold start flap, it closes to route air from the lower intake hose thst goes to your heat source. The connection i think goes to a multi-tap vacuum switch into the water jacket. The hot water opens the vacuum source to the flapper to let the fresh air in after warm up or something like that. Emission stuff had an evap shutter at the same place but it didnt have a lower air entry. The vacuum would open the shutter for run, but close it on shutdown so your carb bowls woudnt dry out into the atmosphere. They work! Neither is critical.
TylerW
Well-Known Member
That's an interesting approach...
The correct arrangement is this:
First, as mentioned, you are missing the carburetor pre-heat valve on the air cleaner. Seeing that you are from the south same as me, it probably got removed by a previous owner because they decided it was a "restriction" to that 100-hp Slant six.
You'll need to fix or replace the air cleaner first. That may not be the original anyway because I think only the later version had round inlets.
Then, flip the air cleaner base over so you see the bottom. There's two vacuum nipples there side by side. That's the thermostatic temperature switch that permits or cuts off vacuum to that flapper depending on the temp in the air cleaner. Cold, vacuum flows and shuts the door, Hot, the vacuum stops and the door stays open.
Anyway, one line runs from that valve to the flapper door in the snorkel. The other runs to a vacuum source at the carb.
In this case, I see that someone has again looped the two connections on the Holley 1920 cause they didn't know what to hook to them. When you look at the left(driver side) of the carb where that loop is, the FRONT port, meaning toward the radiator is where you connect another vacuum line that you install from that thermo valve on the BOTTOM of the air cleaner. Then you are finished with that.
Regarding the other port in that "loop"..the rear one: that is supposed to be connected to the choke pull-off that is about 3 inches above it.
Onto that apparatus mounted on the side of the air cleaner:
That's the OSAC valve. In everyday terms, it's a delay valve for the spark advance signal to the distributor. One side is labeled CARB and connects to the carb, the other is marked DIST and connects to the advance on the distributor.
I normally try to keep things original but that was a poor idea to try to reduce emissions. You can get a slant air cleaner which does not have that thing in there. In fact, through 1973 the OSAC was mounted on the far right of the firewall.
Hope this answers your questions.
To the poster above:
You are probably thinking of the thermostatic vacuum switch that was mounted in the radiator and controlled the vacuum flow to the EGR valve depending on coolant temp. Easy to confuse. Later on that switch migrated to the cylinder head.
The correct arrangement is this:
First, as mentioned, you are missing the carburetor pre-heat valve on the air cleaner. Seeing that you are from the south same as me, it probably got removed by a previous owner because they decided it was a "restriction" to that 100-hp Slant six.
You'll need to fix or replace the air cleaner first. That may not be the original anyway because I think only the later version had round inlets.
Then, flip the air cleaner base over so you see the bottom. There's two vacuum nipples there side by side. That's the thermostatic temperature switch that permits or cuts off vacuum to that flapper depending on the temp in the air cleaner. Cold, vacuum flows and shuts the door, Hot, the vacuum stops and the door stays open.
Anyway, one line runs from that valve to the flapper door in the snorkel. The other runs to a vacuum source at the carb.
In this case, I see that someone has again looped the two connections on the Holley 1920 cause they didn't know what to hook to them. When you look at the left(driver side) of the carb where that loop is, the FRONT port, meaning toward the radiator is where you connect another vacuum line that you install from that thermo valve on the BOTTOM of the air cleaner. Then you are finished with that.
Regarding the other port in that "loop"..the rear one: that is supposed to be connected to the choke pull-off that is about 3 inches above it.
Onto that apparatus mounted on the side of the air cleaner:
That's the OSAC valve. In everyday terms, it's a delay valve for the spark advance signal to the distributor. One side is labeled CARB and connects to the carb, the other is marked DIST and connects to the advance on the distributor.
I normally try to keep things original but that was a poor idea to try to reduce emissions. You can get a slant air cleaner which does not have that thing in there. In fact, through 1973 the OSAC was mounted on the far right of the firewall.
Hope this answers your questions.
To the poster above:
You are probably thinking of the thermostatic vacuum switch that was mounted in the radiator and controlled the vacuum flow to the EGR valve depending on coolant temp. Easy to confuse
. Later on that switch migrated to the cylinder head.Thanks, TylerW! Couple more questions...
I actually had that switch on my radiator and didn't know what it was either. Swapped in a new radiator last week and threw it out with the old radiator. Hope that wasn't a mistake.You are probably thinking of the thermostatic vacuum switch that was mounted in the radiator and controlled the vacuum flow to the EGR valve depending on coolant temp. Easy to confuse
So it's OK if I just cap those off? The only thing I have left on the car is the charcoal canister and EGR valve. I have the vacuum amplifier valve but I don't know if it works or not, it was in the trunk when I got her.
Would that be "ported" vacuum?
Don't suppose that's available as a replacement part anywhere without having to find a whole air cleaner? Got a part number? I see a lot of similar parts on the web.
TylerW
Well-Known Member
1. I try not to throw out original parts if I can help it, they are getting more rare as time goes on. It won't hurt anything to run without EGR unless it just won't stop pinging.
2. You can totally ignore the osac valve. Don't connect any vacuum to it at all.
3. Both of the ports at the bottom left driver-side of the carb are manifold vacuum. Has vacuum at idle and above. The air cleaner, heat/air controls and the choke pull-off use those(the heat/air control taps into the single port at the rear of the intake).
Stuff like the signal for the EGR and it's related vacuum amplifier,the charcoal canister and the ignition advance use ported vacuum since by design those items do not need a vacuum signal at idle.
4. I'd just get an entire used air cleaner from a member here. There were tons of them made and people are probably stumbling over them.
Good Luck!
2. You can totally ignore the osac valve. Don't connect any vacuum to it at all.
3. Both of the ports at the bottom left driver-side of the carb are manifold vacuum. Has vacuum at idle and above. The air cleaner, heat/air controls and the choke pull-off use those(the heat/air control taps into the single port at the rear of the intake).
Stuff like the signal for the EGR and it's related vacuum amplifier,the charcoal canister and the ignition advance use ported vacuum since by design those items do not need a vacuum signal at idle.
4. I'd just get an entire used air cleaner from a member here. There were tons of them made and people are probably stumbling over them.
Good Luck!
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