carb problems

[dodge truck]

I have a 1979 Dodge half-ton 4 wheel drive pickup with an automatic transmission, a 360 CID engine and a thermoquad carburetor (No. 9225). I bought a used carb and put it on and it won't idle. I rebuilt the carb and reinstalled it and it still won't idle. I've tried backing out the idle adjusting screws one turn at a time. That didn't work. I checked all my vacuum hoses. Throttle body isn't cracked or broken. I increased idle speed and that didn't work. How do I get it to idle? Thank you.

 

[demon sizzler]

If your rebuild kit supplied you with a Quadra-Jet base gasket(almost always a brown thick gasket), you will loose the idle circuit. This is because the primaries on the 850 cfm carb that you have are larger than the opening in this area of the gasket. The fuel/air mix will 'hit a wall' so to speak, thus killing the idle circuit. Your base gasket should be a black gasket, David.

 

[dodge truck]

Thanks for the advise.
It was a Wagner kit. It was black (it looked painted). Do I need to do anything to it?

 

[demon sizzler]

It sounds like a real T.Q. gasket and it just goes on the intake flange as-is.
So let me ask you what adjustments you did to the carb to get it to idle:

did you back off the idle speed any? If so, you may have shut down the idle circuit. The way to correct this is to turn the idle speed screw clockwise to get an idle, then back off your initial timing a few degrees. You are essentially setting the idle speed with initial timing.

Here is a pic of the idle transfer slot at the front of the primary bores at factory adjusted specs; shows roughly a square.

**Note that the round upper hole is the idle mix screw hole for the tip and the idle transfer slot is the rectangular slot below. The idle transfer slot should only show roughly a square with the fast idle cam off**

 

[dodge truck]

I haven't been able to get it to idle. I tried backing off the idle air mix screws a whole bunch but that didn't help. What you say makes sense because the primary valves are completely closed when you let off the throttle. Would that cause it to die at idle?
Thanks for your help on this.

 

[demon sizzler]

If the primary butterflies at the front edge have the idle transfer slot covered up
you will have no idle circuit. So you will have to adjust the idle speed screw accordingly and also the initial timing accordingly, David.

 

[dodge truck]

OK, I made sure the idle transfer slot is not covered up, but the problem persists. I noticed that if I open the choke valve even a little it dies. Does that indicate a vacuum leak? Or something else?
Thank you.

 

[mullinax95]

OK, I made sure the idle transfer slot is not covered up, but the problem persists. I noticed that if I open the choke valve even a little it dies. Does that indicate a vacuum leak? Or something else?
Thank you.

Borrow another carb from someone (Holley, Edelbrock) and try it. If it still dies then it's something other than the carb.