We have had a handful of people ask, How can the MSV Racing ’85-’01 CR500 OptiFlo H2O pump cover add +1 GPM more coolant flow over the OEM or billet replica covers using the “phi” Impeller?

Here is a cutaway showing the reason. The full radius smooth flow path into the “phi” impeller. This greatly reduces turbulence into the impeller. Take a look at an OEM covers flow path and you will see the huge difference. Also there is much tighter clearance between the cover and impellers flutes. This reduces impeller churning enhancing coolant flow.