Quote:

I bought a heli-coil kit for a #12-28 to fix the thread. But now I use a High Flow squirter screw for flow.
The existing design might have a groove machined parallel through the threads. This is how the squirter got the fuel. But the heli-coil covered up this groove so I went to a hollow screw.

I think the O.P. might be talking about the screws for the pump not the nozzle.

In theory, there is no difference between theory and practice. In practice, there is.