My Holley 1830-3 has both float valve screws all the way down but fuel still runs out of the level plug holes with the engine stopped and the pump running.
Are there different lengths? They don't seem worn.

 

Check your needles. They are probably letting fuel still get in.

 

Just a couple of things to consider.

Remove the bowls and make sure that the floats move freely. Also, make sure that the floats aren't leaking (filled with fuel).

The external float adjustment may not have enough adjustment range because the float arm is bent.

http://forums.holley.com/entry.php?4...el-Carburetors

 

Do you have your pressure regulator set at the right pressure?

 

Not sure where the pressure regulator is.
When the chamber is off, the float when up is about 15 degrees above level.
The float seems empty.
It looks like the jets are too short.
Does the engine need to be running?

 

If you are running a electric fuel pump you should have a regulator. I would get a fuel pressure gauge and check your pressure. A Holley carb should not have much more than 7psi. You may have to much pressure and the needle and seat can't stop the fuel flow when it reaches the proper fuel level.

 

I got it now. I had not understood how the adjustment actually worked. Should it be done while the engine is running or static?

 

I would do it with it running

 

Should there be an adaptor plate (pn 20-121) for the th300? It is connected directly at the moment.