(Warm) Air intake hose

-

SlantedMark4

'74 Valiant 225 /6
FABO Gold Member
Joined
Nov 3, 2022
Messages
111
Reaction score
54
Location
Switzerland
Hey guys
Short question: There's this intake hose from the engine block to the air filter box to warm up the carburetor. What's the part number of that? Or does anybody have a link?
Also, driving without that in warm weather won't do any damage I think?

1974, 225 Slant Six, no mods (Delaware plant)

IMG_20240425_181301.jpg


IMG_20240425_181312.jpg
 
I'm pretty sure it's just there to aid in cold starts & don't think it will do ANY harm not having it, as a lot of people got rid of them anyway. It's just flexible ducting & most auto parts stores or hardware places have similar ones. I don't know the factory part number but, you can run without it, no problem.
 
If you can't find it elsewhere, try locating the heater duct that goes to the defroster vents that is the correct diameter. I got some at the local NAPA for a pretty decent price.
 
Chrysler part number for pre-heater hose is 3577808 which supersedes to 4039020. Both numbers show Dorman 96034 as an interchange.
Dorman 96034 can be found on eBay and Rockauto. The Dorman number can also be ordered at most auto part stores.
 
Warm air duct conducts heated air from the exhaust manifold 'stove' in an effort to provide a more consistant air intake temperature.
and yes, faster warm ups.
The vacuum diaphragm (aka vacuum motor) usually is controlled by an air temperature sensitive valve in the air cleaner housing.

Described on page 2 of the '74 Cleaner Air System
 
The low to intermediate circuits of your carb are calibrated to work at a prescribed inlet air temperature.
In your air-filter housing are a temp sensor, a mixing valve, and two large hoses; 1) the cold air duct going to in front of the core support, and 2) the other to a scoop on the exhaust manifold.
That system is designed to mix hot air from off the manifold with cold air coming in thru the cold-air pipe, to the create the specified temperature..
Can you defeat the system?
Yes but, yur gonna have to recalibrate the main metering system.
xxxxxxxxxxxxxxxxxxxxxxx
If you defeat the system, without re-calibration:
The carb will run lean when the ambient temp is below the set point, and rich when ambient is above the specified set-point. But usually not enough to hurt the engine.
>Around town, you may never notice a difference, because the system drops out of operation when the manifold vacuum drops, due to a large throttle opening.
>But on the hiway at a steady throttle opening, fuel economy will suffer, unless the ambient is at or near the set-point.
I forget the setpoint just now (I'm getting older) but I imagine it would be, at some logical and easy to maintain temp like maybe 100*F; I'm guessing.
the most noticeable sign of lean-running is
> a tip-in sag, aka a hesitation, from a dead-stop.
> lousy gas-mileage, due to the throttle having to be opened further than necessary to get the fuel, to get enough power, to attain cruising speed.
Other signs could be;
> overheated sparkplugs
> burned exhaust valves
>possible coolant overheating
> possible pre-ignition, leading to detonation, sometimes ending in broken sparkplug insulators.
> an overheated exhaust manifold leading to cracking.
 
Last edited:
Helps prevent/reduce carb icing in cold weather .
And for anybody who thinks this only happens in northern climates I had it happen when I lived in Houston in the early 80s, just pulled to the side of the road and let the car idle for a few minutes and the ice on the venturies melted and the engine ran normal.
 
There are 2 pieces to this set-up, the air motor out on the air intake (shown in your picture) and the temp sensor thin which is located on the air filter housing in the bottom side. It will have 2 vacuum hoses connected to it, one going to the vacuum source the other to the air motor. In my experience the air motor hardly ever fails, the other thing often does. It’s easy to check, hook an air hose directly from vacuum to the motor, if when you start the car it will close the lever regardless of temp. If the air motor is good you need the other piece. They turn up on eBay all the time, but there are different units for different years/ models. Here is one that is on eBay right now- Carter TS10 Air Cleaner Temperature Sensor For MOPAR 3514168 | eBay

Good luck!
 
You can also test the motor diaphragm with a handheld vacuum pump and see if it operates and holds vacuum. You can also test the sensor with the same vacuum pump and a hair dryer although you won't know the opening temp but at least you can prove function.
 
-
Back
Top