Take this with a big jar of salt... I had a 1406 on the front and a Carter performance 625 CFM on the back... I would just get them the same and was very much experimenting... I just now remembered and went out and took a picture of my garage door from when I was setting them up and where the AF gauge was and how it would run.. mind you I've sold those carburetors and went a completely different way... Maybe is for a baseline starting point...