Are Underdrive pulleys worth buying?

I just installed plenum and TB. I can tell a minor difference, but IMO the pulleys seemed better. I only paid 330 for the Plenum and TB, but I paid about 160 for the pulleys on ebay. You should definately get them before plenums - dont forget they improve fuel economy.

If you are thinking about pullies here is some advice from www.bullittarchive.com

Under drive pulleys
Selling points

* More of the engine power is available by using driving the accessories at a slower rate than normal.


Things to consider

* The vehicle is engineered to work from the AZ desert to sub zero temps in the northern states. Perhaps you are able to slow your water pump and alternator down with out a problem. Just remember that the entire cooling system was engineered on how much heat your engine makes, how much HP it produces.

* If you start adding power modifiers AND under drive the accessories, this may be a recipe for problems later.

* If you find your self mainly making a lot of short trips and idling for extended a period of time, then under driving your alternator may be a problem later also.

ALSO:

14520
4.6L Pulley Instructions
Some 1996-2001 Mustang owners, for engine performance purposes, are adding a special front drive pulley kit to reduce front accessory drive speeds. When removing and replacing the crank pulley, if the large bolt used to hold the crank pulley undertorqued, the keyway will shear and cause major engine damage. The resulting engine damage is not warrantable. If the crankshaft pulley bolt is removed it should be replaced as it is a torque to yield bolt. The installation of the crankshaft pulley requires that a specific torque operation be adhered to. The crankshaft pulley bolt must be installed using these 4 steps: 1) Torque to 75 lbs/ft 2) Back out one turn 3) torque to 45 lb?ft 4) continue to tighten and additional 90 degrees.

streetstang03 said:

i never could understand paying 200 for ~5hp. or spending 500+ for a plenum and getting 8hp waste of money IMO. i would save it for cams or gears

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Great everything on my car is a waste of money then.