I am in the process of rebuilding a Holley NH. It's almost completely disassembled except for the main jet, which has a screwdriver slot in it and I'm sure it's removable.
1. It's being very stubborn. What's the best way to remove it without messing it up?
2. The jet appears to be in good shape - is there any real need to remove it, or just clean and leave in place?
Hit it with some 50/50 acetone/ATF and let it set a bit. Then I'd make sure you have the biggest possible screwdriver that fits down in there.
Warm the cast iron up around the jet with a plow torch, let it cool and the brass jet should screw right out!
unless you plan to replace it or replace the gasket, leave it alone. Just soak in carb cleaner and blow it out with compressed air. You run the risk of damaging the jet or the seat in the casting. I've seen cracked threads which ruin the carburetor.
What's a plow torch ?
Sorry Bud should have been blow torch, that's just an easy name we use for a oxy-acetylene set, even if you had a propane torch for heating a soldering iron would do the trick, doesn't take a lot of heat, not red hot as the brass could start to melt at that temp.
Thanks for the info.
Just thought this is a plow torch.