what exactly is this and what is the benefits and the disadvantages of these?

just wanting to learn so any help will be appreciated.thanx

 

I don't have any experience with them on my truck but they way I understand, most are lighter, which will require less horsepower to be robbed when turning the accessories. Some are also bigger or smaller making the engine not have to work as hard to turn over the accessories. The only really bad thing I can think of regarding underdrive pulleys, is do not skimp on cheap ones, I have seen crank pulleys that have the balancer built in that are not properly balanced cause premature engine failure due to the enging not being balanced. I don't know who makes pulleys for our trucks but ASP, March and BBK are good manufacturers.

 

ok so what all pulleys come with this kit and can you still use the same belt and does it affect your a/c?

 

Underdrive pullies are smaller. Overdrive pullies are larger.

If you only do the underdrive crank pully, you decrease the efficiency of your water pump, power steering, and alternator and air conditioning.

In my opinion, they're not a mod that should be done ahead of more basic mods like a cold air intake, throttle body, and exhaust headers. They offer a very minimal gain, especially for the cost.

IIRC, Mopar Performance does (or used to anyway) make a set for the 318 and 360 magnum motors.


EDIT: You also generally need to get a different belt.

 

ok so there is a underdrive and overdrive which one is a performance mod the underdrive?

 

Depends on what kind of performance you want. If you road race, or have a big stereo, you would want overdrives for your power steering and alternator respectively. If you want to get every single horse out of your motor, you want underdrives. Like I said above though, I wouldn't recommend them ahead of other mods that will give you much more for your money.

 

if you want to help get rid of friction and forces holding the engine back.. you should maybe look at that big metal fan its trying to spin.. a electric fan mod would give you a much better preformance gain that just messing around with pulleys

 

also the pullys for the 5.9 and 5.2 are a bit different.. something to keep in mind when/if you want to buy one.. specifically the pully for teh crank.. bolts on differently for each motor..

the only pully id recomend changin is underdriving the ALT pully.. since your alt doesnt produce its advertised amp output untill 1500 to 1800 RPM.. underdriving it would hvae it spin at higher rpm's at idle or just above idle.. like rom said.. there are better mods to do when you have a stock truck first then underdriving stuff..

 

True. The 5.2 is internally balanced, while the 5.9 has an external balancer built into the crank pulley.

 

how much would a pair of electric fans run? and wouldnt u have to rewire for the fans?