What exactly is an underdrive pulley, and is there any benefit to installing one? Dealing w/'88 F150, 351W/C6.

Thanks!

 

An underdrive pulley is a smaller pulley to replace the crankshaft pulley. This will slow down the rpms of your accesories thus decreasing the amount of power it takes to turn them. I think most people install them just to have nice shiny pulleys but they do increase HP just a tad. Sometimes you can have problems with over heating and undercharging at idle. Ask someone who has the same pulleys on the same vehicle and see how they like them.

 

Possibly look for a "street set". These are 3 pulleys. An underdrive crank pulley, an overdrive alternator pulley and an overdrive water pump pulley. The net result is the alternator and water pump are still underdriven but not as much as the other accessories (power steering, AC, smog pump). I assume the power gains are less in this system but have fewer side effects of potential overheating and low/no alternator output at idle.

Randy

 

I have underdrive pulleys on my 5.8L, only the water pump and crank pulleys. I didn't get the alternator pulley because it causes the alternator to turn too slow, giving you the dim headlights at a stop light and the under charged battery. I also have an electric fan, to replace the stocker (which is your biggest power thief in that area). Changing the stock fan for an electic version will free up quite a few HP, helps the water pump to last a little longer and avoids that annoying overheating problem.

 

By turning the water pump slower this gives the water a chance to absorb the heat in the engine. At high rpm's the water is going through the block and heads to fast to pickup any heat. That's also why lots of the holes in your head gasket are way smaller or closed off to restrict the water or devert(sp?) it.