How much performance gain can be expected from these two? Whats the better one? Are they worth it?
Dave

 

Fan would be the best way to go. Less work the motor has to do. The pullies would run a chance of slowing the alt. down to the point it won't charge when at a stop light. I have heard that the elec fan gives roughly 7-10 hp back.

 

Plus the electric fan removes weight from the water pump and stress on the water pump pulley...I put two 14" PermaCools on mine and it keeps it cool in the hottest situations

 

slikness - can you feel anything in the throttle due to the loss of the regular fan? Does the motor responde better? Stronger? What about mpg? I'm thinking about electrics for my truck and I'm mostly interested in mileage and a little extra power.

1994 Black/Silver F150 XLT 4x4 Reg Cab / Short Bed, 3.55 LSD, 5.8L w/85k miles, K&N drop-in w/bored out airbox
Upgrade wish list: 31x10.5, Gibson exhaust, helper springs, lights, electric fans

 

Yeah, I felt a tremendous surge in power...oops, maybe that was the swap from the 300 I6 to the 351W...sorry, I went to electrics when I swapped engines, so I can't compare....however, we swapped out the clutch fan on my son's Pure Stock 4 cylinder stock car (oval track racer) and we found an imediate gain in the rpms...I believe we were able to spin the motor up quicker coming out of the corners, which gave us a couple hundred more rpms at the end of the straight...

 

The underdrive pulley will not charge at the stop light but as long as you have a good battery and don't plan on idling for over an hour, there won't be any driveability problem.