Carb Assistance

[Nitronick]

Once you go back to idle for a short period of time it's like nothing has happened.

This is the indicator that you should look elsewhere. There is nothing in the carburetor that changes after you go back to idle for a short time.

 

[Bob Chadwick]

What about the level of fuel in the float bowl. Wouldn't higher speeds use up the fuel faster and possibly be impacted by the float adjustment or fuel pressure issues?

 

[Nitronick]

try opening the idle mixture screws several turns to richen up the carb because the idle feed continues to fuction at any speed.

I've got to disagree with you on this, motorman.
Depending on what carb and idle circuit we are dealing with, the idle circuit is bypassed after a certain rpm level is reached. The atmospheric pressure change switches the fuel draw from the idle circuit to the main jets.

 

[motorman]

I've got to disagree with you on this, motorman.
Depending on what carb and idle circuit we are dealing with, the idle circuit is bypassed after a certain rpm level is reached. The atmospheric pressure change switches the fuel draw from the idle circuit to the main jets.

the idle feed and the idle transfer slot are fed by the main well and as long as there is air passing by the discharge ports it will pull some fuel thru them. it depends how far open the butterflys are how strong the signal will be.

 

[Nitronick]

What about the level of fuel in the float bowl. Wouldn't higher speeds use up the fuel faster and possibly be impacted by the float adjustment or fuel pressure issues?

The float level is a static setting. It is set for when supply exceeds demand, ie: at idle, you are not using much fuel, but the pump is still pumping. The fuel level raises the float which in turn lowers the needle into the seat, blocking fuel flow into the bowl. The float level setting does not change unless you change it.
Fuel level is a different thing. If your pump is weak, it can allow the fuel level in the bowl get low at higher speeds, possibly even draining the bowl. Demand exceeding supply. That is not a carburetor problem, but a supply problem. Unless, of course your float level is set so low that it only allows a small amount of fuel into the bowl before it closes the needle and seat. But in this scenario, you would see drivability problems long before you reached highway speeds.
If I'm not mistaken, a 1977 has a mechanical fuel pump, correct? Any fuel pressure problems are going to be caused by the pump or regulator if one is present.

 

[Bob Chadwick]

That's what I meant.