i have a 305 thats stock except for hedders and intake,and a 625 road demon carb.it idles and revs great but when im driving and stomp it,it tries to stall until i back off.i know i can unhook the four barrell but can i turn the gas down if the motor gettin to much?

 

Gm used the Qjet on some 305's and they are 750's, so I don't think you are overcarbed. Look at your accelerator pump shot or the secondary opening point. Is that Demon a double pumper? If so....

I always prefer vacuum secondary.

 

See if it has that vacuum diaphram on the side. If so you should be fine with that. If you accelerator pump is working right then you may have to soft of a spring in the diaphram and it is allowing the secondaries to open to quickly for the breathing capacity of the 305. If it is mechanical secondaries then that could be a problem with an automatic with stock stall converter and typical stock gears.

 

IS the choke open? My Holley 600 has an electric choke but sometimes it sticks shut very tightly and anything past 1/4 throttle is terrible. I have to stab at i with my finger to open it. Goodluck!

 

<Note to self: Keep the tuned port injection )

 

Yeah, keep that fuel injection system where the cost of merely replacing ONE sensor is greater than buying a brand new intake manifold and carb together

 

Or you could just have the worst of BOTH worlds!

 

I wouldn't go any bigger than a 650 vaccume 2ndary (any square bore) on a stock or near stock 305.
Look at the secondarys sound like to much fuel.
Have some one fallow you and hit it and have them look out for black smoke.

 

625cfm is about right for a near-stock 305. As stated, make sure the secondaries aren't opening too soon, and check your accelerator pump.....sounds like its just shootin too much fuel.

 

Aren't the Road Demons' mechanical secondary's?
I agree with too soon openining secondaries killing the port velocity and falling on its face.
Try rolling into it until a higher rpm then stab it. If Ok then, we're right...

Also a great near perfectly self calibrating overlooked carb for the street is the odd looking "Predator" carb. Only a restriction when used in big cube or hot performance app's.

 

I beleive road demons come in both mechanical and vacuum. Easy to tell though by looking.