75 Chevy 400 SB cooling issue

[Bluestep]

Dan, I am glad I was able to help you! It is a lot more fun when your vehicles are working well!
In Weiand's defense, they offer their pumps with or without the bypass port. It just doesn't make much sense to put one without a bypass on a street driven vehicle. It makes it difficult for someone like yourself to try to figure out all the modifications that took place before you bought it.