Originally Posted by carlk4728
I'm finishing up my 1974 454 swap into my 87 K10, and am having some trouble with fuel literally spraying like a fountain out of the top of my carb when I crank the engine over. The carb is a later Quadrajet that came off of an 85 small block that I sent out a year ago to be tuned and modified to add a little performance.
I can send the carb back to the shop to have it looked at, but before I do that I want to make sure that a second modification, one to the fuel pump, is not causing this issue. I wasn't able to get the stock mechanical fuel pump to clear the frame rails, but I was told that a pump from an early 70's biscayne with a 454 would clear and work. It does fit, but it doesn't have a return line on it like my old one.
Is it possible that this pump without the return line is building enough pressure to overcome the float/needle and seat in my carb? Or is it more likely that the carb is just rebuilt improperly?
Unless the pump you just got is somehow defective, the pressure would not be enough to cause the needle and seat to be overpowered. But there could be pressure built up in the fuel tank if the system is unvented. You can try removing the gas cap and see if there's a difference, but I doubt that's it.
Likely, something has fouled the needle and seat: a string of teflon tape from the fuel line fitting or carb filter housing would be a prime suspect.
If you want to take the time to do it, disconnect the fuel line from the carb, set it aside. Install another fuel line fitting w/a short length of tubing connected to it (or a hose barb fitting) and see if the needle and seat are holding pressure by connecting the line to a fuel source held above the carb. This could be a mower gas can and a length of rubber fuel hose. Get the fuel flowing by siphon, connect the line to the carb and see if it still overflows.
Or take the top off and have a look-see. Or return it for them to deal w/it.