I am trying to lean the mixture so I can pass emissions. It is a 73’ Dodge van rv. It has a 440 with the 2 barrel carb(assuming it’s a carter). There are two forward faceing adjustment screws, which is fuel?
There are two forward facing screws, one for each barrel, exiting the base of the carburetor with springs on the shafts. These were interference caps on them from the factory. If the caps are off, turning the screws clockwise leans the mixture, counterclockwise richens. It is not likely that turning those screws will accomplish much though. The screws have little effect on the fuel flow above a fast idle. If there is black exhaust and the engine is surging at idle you may need to replace the carburetor.
Both of the screws are the fuel mixture screws. To set the fuel mixture, with the engine hot but not running, turn the fuel mixture screws all the way in until they seat. Then turn the fuel mixture screws out three turns. Start the engine and turn one of the mixture screw in until the engine starts to stumble and then turn the mixture screw out until the engine smooths out. Repeat on the second mixture screw.
Wow, they only put a 2-bbl on a 440?
What were the numbers from the emissions test? Is the engine running poorly?
I would start at 2.5 turns out… Adjust the idle speed to 650-700 RPM. Set the timing and dwell FIRST. Turn one screw in slowly until you detect a slight RPM drop. stop turning. Repeat with the other screw. This is called the “lean drop” method used by Chrysler during this time period…When you are finished, the RPM should be down 50 from where you started but still idling smoothly.
I agree with Rod. First tell us what the emissions readings were and we can be more help.
I can’t imagine they have to put a motor home of that age through an emissions test but whatever I guess. While that is the proper way to adjust the carb, on that vintage, it still was not always possible to lean it out enough and you had to bump the idle speed up some and then lean it out some more. They would be so lean they would diesel when shutting them down so also had a shut down solenoid to let the throttle close further. So once you pass emmissions, go back to the method described above.
The mixture screws only control the air/fuel mixture at idle so how is this van failing?
HCs, CO, NOX?
Believe it or not Oblivion, they even had 440s come out of the factory with one-barrels on them. (Mid/late 60s station wagons I think. It was done to improve the low end torque and get that battleship mass rolling from a stop.)
I have never seen a Chrysler 440, Dodge motor-home or whatever, that did not have at least a big 4-barrel on it…Some had two 4-barrels…A few had three 2-barrels…But they ALL had at least a single 4-barrel…
There was no 440 engine available on the '73 model it appears. And from '74 until '78 all 440 engines in Dodge trucks were 4bbl. My source was a Motors manual from 1978 for model years '66 through '78.
I’m still wondering what the readings were. It’s entirely possible that a carb adjustment is not the solution. Over the years I’ve seen people try adjusting carbs to solve all mode of problems that were not carb problems to begin with. Just as bad gas is unjustly claimed for so many problems, so carb adjusting is tried to solve all forms of problems.
I hope we hear back from the OP.
I have a 73 dodge van RV winnabago with a 360 (I think) and a 2 barrel carb. I rebuilt it a few years ago and I have been working to get her running again. Just replaced the fuel filter and pump.Coil and plugs. I’m also having a carb problem. When the engine is running and warm its running great. If you press the gas pedal you can see 2 streams of fuel while it’s running and borfore starting. However it’s very difficult to start cold and somewhat difficult when warm. Cold, if I splash some fuel down the carb it starts up right away…
Any ideas how to improve the starting preformance? Is it too lean? Do I have to do another rebuild? Could it be anything but the carb?
Sounds more like a choke problem. When the engine is cold, one press of the gas should close the choke completely. Then, as the engine warms up, the choke should gradually open. Sometimes, the linkages stick and the plate doesn’t close. A generous cleaning with carb cleaner may get them working freely again.
The main controller of the choke should be a plastic disc attached to the side of the carb. Inside is a coil spring. If the coil is cold, the choke springs closed. As this coil heats up, the spring relaxes and opens the choke plate back up. Loosening the three screws that holds the plastic cover on, and rotating the disc is how the choke adjustment is done. If the spring is broken, then it can be replaced without replacing the carb.
The plate at the very top of the carb is the choke, jut in case you did not know. The throttle plates are at the bottom.
Tnx, I have a divorced automatic choke and i havee tested that it gets power to heat the bi-metal spring and also tried to adjust it. I have an international scout and the choke needs to be slieghtly open about 1/8 or it won’t start cold. Just to confirm, are you suggesting the choke plate should be adjusted to the FULL closed position when cold?