U/D pulley Questions

[ccrunner1]

who has em?
do they really help?
any negative effects?
how hard is it?
do i need to buy a diff length belt?
do i need to remove the fan, or can i just go from under my truck?
what tools do i need?
any thing else i should know?

 

[Mutant Pony]

Underdrive pulleys were originally designed for racing. At higher RPMs the water pump is turning too fast to function properly. An underdrive pulley slows down the water pump so that is functions at those higher rpms. The fact that it frees up hp is just a side effect.
If you never get your engine into higher rpms you don't need the rpm reduction at the water pump.
It also slows down the alternator. You could end up with low output or no output from the alternator at idle.
There is nothing to installation. Remove the belt, unbolt the lower pulley (4 bolts), bolt the new pulley on, Install the new-shorter belt.
Many people have installed the 3.0 underdrive pulley and had NO problems with overheating or charging.
It is available from Underdog performance. There should be a link in the "technical library" or you can go to RPS and find out even more about it.