I have a '24 Canadian with a Holley NH. It is has "Made in USA" stamped on it along with the number 15. I have no idea if that is an original carburetor. I think it one of the few things that does not have made in Canada stamped on it. Just out of curiosity, does it sound like an original carburetor? Also the casting looks a little different than what I have seen on other NH's, especially in the tube that goes into the float bowl. This one has two brass plugs in that tube. The other ones I have seen only have one. I am pretty much a newbie, so the number I have seen is limited. Next question, is there another plug under the name plate? It looks like there is, but thought I would ask before removing it. Thanks.
Yes, it's a regular NH. There were slight changes over the years. Some have the bottom plug shown in your picture, and others have only the three higher ones. Either way, they're all openings to the same passage. After you drill them out to clean the passage you can replace them with brass rod as original, or you can tap the holes and install 8-32 set screws to facilitate removal for cleaning. A good clean-out tool is a brass-wound guitar string. The hole under the tag is an air vent, and is unplugged.
Tim: No plug under the plate so don't remove the plate. Remove spray needle seat and access that passage from inside. jb
Thank you for the information!