Intake An Heater Fitting

[331turbo]

I have a victor jr intake converted to EFI. I am replacing factory heater core line (steel one) with AN fitting an alum tubing. My question is this the lower intake heater hose what is the tread size? From what I have found a lot of people are running 1/2 NPT treads. I plug the lower heater hose line back when I did away with the heat. But I noticed when I remove the brass 1/2 NPT plug the thread in the towards the top were the brass plug was were smoother then the thread at the bottom when the plug did not reach. This makes me think that it is not a NPT thread type but just standard threads. I also recall having to fight it some to get it to seal an stop leaking. Anyone who has replace there with a AN fitting with NPT did you have to tap your lower intake to make it work if not what did you do. Thanks

 

[331turbo]

Can delete thread it is 1/2 NPT threads.