I have heard that Manley Pro-Flo valves really help low lift flow, and I am very interested in them. However, they are almost twice as expensive as Street-Flo valves which are advertised as having the Pro-Flo underhead feature. Does anyone know if this feature (the underhead angle) is in fact the key to the increased flow? Since the valves are intended for a street motor I don’t want to pay for fancy race features that I may not need.

 

They both have the undercutting and necked-down stems, difference is in materials wherein the Pro-Flo valves are stronger. Unless you do major racing or run obscene valvespring pressures, the Street-Flo valves are more than strong enough.

 

Excellent. Thank you.