I wonder if the differences in choke linkage that you mention, is between the original super six BBD and the Holley replacement carb for the BBD.

The carbs in the picture are correctly tagged, you can clearly see the difference in the width of the straight section of the top edge, the wider is for 225s.

Olaf.

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Aspenized

I just did all of the adjustments listed in the FSM for the carb. Put it back on, warmed it up, set the idle. My mixture screws almost seem to do nothing. Enriching the mixture with propane only makes the idle slow. The car is still running very rich, noticeable by smell and soot left on the ground behind the tail pipe.

I'm stumped why this is still running so rich, I'll try re-lashing the valves .12/.22 again today to see if that changes. If I'm really that bad at lashing the valves, would it cause this bad of fuel economy?

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1978 4 door Dodge Aspen, Super Six

Try turning the idle mixture screws all the way in. See if that makes a difference.

If you have BBD with a 318 main body, the venturies are bigger than in the 225 main body, and if your vacuum signal is a little weak, you may experience some difficulties in setting the carb absolutely correct.
On the other hand, the idle circuit has openings around the edge of the throttle blades, and should not be influenced by problems at higher RPMs.
I know you have read up on these carbs, but do you know if the throttle body is for a 225 or 318? There are restrictions in the idle fuel channels in the 225 throttle bodies used on the super six from '77 -> up, and the setting for the fuel mixture screws has a limited effect compared to other BBDs.

Could it be that you have the throttle body from another carb?

Or that someone has opened up the restrictions?

The mixture screws are also different between super six and other BBDs, see pics in bootom post in this thread: Carter BBD Setup

Olaf

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Aspenized

I have switched the throttle body to one from a 318 BBD since the 225 BBD on the car when I bought it had a very leaky throttle shaft. The Main body of the 318 BBD I have has a damaged vacuum nipple that goes to the vacuum amplifer/EGR. There is also no bowl vent on the 318 main body.

So to recap, I have a '78 or '79 truck 225 BBD air horn and main body with a '77 passenger car 318 BBD's throttle body on the car. I have not switched any components from one throttle body to the other, the mixture screws are the ones originally on the 318 BBD.

I am pretty sure both of my BBDs have the mixture screw on the top picture, I can check that as well. Are the restrictors visable with the trottle body removed?

I can double check the sheets I have at home on those years. The 225 BBD did not have an ID tag on it, I used the rod and jet part numbers to ID it.

Does this throttle body swap come with undesired results? I could just as easily run the 318 on there with all it's parts now that I understand the chock linkage better.

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1978 4 door Dodge Aspen, Super Six

Did you verify that the various castings you are using have matching internal passages? The BBD was produced for a large number of years with many internal differences and differing passages in the body. That is why the rebuild kits come with so many gaskets- so you can match the gasket to the passages in the carb body. My first suspicion is that either a gasket doesn't match the passages or the passages don't match. At this point my recommendation to you is to get the throttle shaft rebushed on the 225 BBD throttle body and then run the complete 225 carburetor.