This may be a bit of a long shot, since itÆs been a few years since I have had the Holley 4150 series on my Ford apart, so I canÆt remember all the details of the guts. I have recently been inside the carbs on a handful of my yard equipment engines though, and all of them had a little wire clippy piece connecting the float to the needleà Should there be one connecting the needle to the float on the Holley? I honestly canÆt remember, I am just throwing the idea out there.

If it were me, I would pull the needle and seat out and look at them, and see what I see. Maybe there is a bur, or a piece of debris, or something in there that is hanging things up that could be cleaned up.

I wouldnÆt ever put anything in a carb ôthat might help prevent stickingö other than fuel, or carb cleaner though.

I am surprised the fuel pressure is not enough to push the needle down though, are you sure the inlet to the secondary bowl is not plugged with something? Thinking since the carb is ôrelatively newö maybe there is a piece of shipping/ packaging debris that is between the fuel inlet tube and the bowl, and it is just too big to pass through, but its small enough to move around in the fuel tube area and sometimes plug things up.

Like I said, if it was me, I would be taking things apart and taking a look.

Sean