What are the pros/cons of underdrive pullies?
What HP gains do they get?

 

Pros: supposed to have less drag from the accessories than the stock pullies, which frees up power.

Cons: You won't see/feel a noticable gain on a fairly stock motor. I did not, nor have I heard of anyone w/ a thirdgen who has. Unless you get the March Power and Amp pullies, your alternator will not charge the battery as well as before.

Supposed to free up 5-15 HP, I'd guess maybe 5 on our cars in stock form, maybe. I'd look for some other mods first and get these when your engine is reving higher and making more power, then the gain might be more noticable.

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89 IROC-SuperRammed 355 w/ AFR 190's and LPE 219/219 cam-http://www.geocities.com/buckeyeroc

 

I had the March underdrive pulley system without the Amp feature. When idling at 750 RPM, the alternator would drop voltage output. When RPM increased just slightly, the voltage came right up. All this with no accesories running either. I did however like how it effected the steering. Obviously the steering pump was turning slower, and therefor had less power assist, which resulted in a stiffer steering. I can only compare it to trying to tie your shoe laces with gloves on, then taking them off. It just felt better, yet was not the arm strong steering of old. For this reason alone I would get the underdrive pulleys again, though with the AMP feature. They will also effect the air pump, obvious waste of HP, but will also pump less water. So if you have overheating problems, Deal with those first, or the underdrive pulleys could be disasterous. I was happy with the March powder coated pulleys, and they were the cheapest, not to mention the best, I think. Although the Coating did start to come off the edge of the alt pulley where the serp. belt goes on.

 

I guess if you have a insane stereo
system like mine.. underdrive pullies
could be disastrous for my voltage.