Cooling Issue

So, after some searching, I can run a 2-1/8" deep w/p pulley and it'd line up with the front 7-1/4" power steering groove (not being used) on my existing crank pulley. After searching ebay, I see they've got 2-1/8" deep single water pump pulleys of the following OD's- 5-5/8", 6", 6-1/8", and 6-1/4". Which one would be best to run with a 7-1/4" crank pulley? Seems the 6" would result in a 20% over-driven water pump. Is that too much?


The issue with water pump speed is the highest RPM you run. If you are below 7k you can run 20% over pretty easy. When the belt speed gets high it will toss the belt. You can help this by using a belt that is thinner than OE to make it fit further in the groove. Then it has more distance to climb before it can jump out of the pulley.

I'm getting about 17.5% with a 6 and a 7.25 but you should be golden.