engine fan questions?

[mikes4692003]

is a clutch fan better than just plain fan ,and is big pully on water pump better than small one  seven blade fan any good

[John_Kunkel]

The fan clutch allows the use of a larger fan blade with more aggressive blade pitch which will move more air at low speeds. Seven blades are preferred when using a clutch.

A water pump pulley that is larger than the crank pulley will slow down both the pump and the fan, this might work in some situations but not all. Also, there are different factory water pumps, some have a 6-vane impeller and some have an 8-vane impeller; the 8-vane impeller is normally driven at near crankshaft speed while the 6-vane pump is usually overdriven about 40%. When driving the pump faster than crankshaft speed there is a danger of cavitation, the smaller impeller helps prevent this and the overdriven pump increases the fan speed for more air flow.

[Paul G]

Question; 6 blade fans, do they actually increase air flow and cooling over a 5 blade, when using a clutch? Summit has several 6 blade fans listed. Just wondering if that would help cool it down, or not.