For this experimental water pump upgrade, I would first like to talk about the PPE!
Must haves!
Leather Gloves (Prevents metal slivers in hands)
Air tight goggles (Prevents slivers going in eyes)
Respirator (Prevents breathing in metal particles and toxic gas from Carbide)
Cheap painters suit (Prevents metal shavings getting on clothes and head)
Now let’s talk about the pump! It is a 251-603 #19168609 For a 2000+ Gm. I call it experimental because there is less then a handful that have done this modification and only a few sites with info about it. Also, I have never done porting before and not sure if is going to work. So for me it’s totally experimental.
The source of information I gathered in regards to this upgrade is found here in these two sites:
https://www.65turbogarage.com/stop-65-overheating.html
https://www.dieselplace.com/threads/251-603-waterpump-porn.561466/
So I got lucky on eBay. These pumps usually go for $200+ but I found an old new stock one for only $100. It’s new but been sitting on a shelf for many many years. AKA old new stock! Lol! The impeller is about 4 1/4” and it has 6 blades. Instead of a bolt on pulley, it has a pressed pulley. From what I read, it pushes out 130 gpm just like the 97+ but it has a 50/50 balance unlike the 97+. Assumed and sounded good to me! Let’s try it!
The end of the cast seems a lot smoother where the big coolant/radiator hose connects. This smoothness will help prevent leaks compared to the Oem 80’s pump cast.