im considering getting a set of underdrive pulley's for my 1986 z28 with a/c. what is offered out there, and what is usually in the kit? its it really worth the $150 to get a little more power? and the most important question, do i have to get different sized belts? (i just bought new ones)

 

If You install different sized pulleys, You'll have to change the belts.

 

Some of them come with new ones!

 

It's absolutely worth it, not only does it free up power lost to parasitic drag, but it also will extend the life of your belt driven accesories by decreasing how fast they rotate and thereby reducing wear. Go for it.

 

If you are running a heavy electrical load, you will have problems keeping the battery charged. Better gain would be to use an electric water pump and electric fans, and leave the pulley size alone, so that the other acessories will work properly.

 

A high output alternator with underdrive added to that combo would likely solve the problem of amperage loss, though. It might cost a bit more, but it'll provide the best reduction in parasitic losses.

 

Also Optima Deep cycles would help.

 

For the small gains (discount the MFG claims) the installations of underdrive pulleys is not worth it on a street driven daily driver. Biggest problem is electrical.

 

im leaving everything electrical stock. im not adding a stereo to it (i already have a car with one), and i might add fog lights in the future. i was looking to get them sometime towards the spring when i have some extra money and the weather is nicer. i really dont want to have to buy new belts, but i would beleive i could sell the old ones on ebay. how much shorter of ones would i have to go to?

 

Really deppends on how underdriven the accesories are. The manufacturer of your pulleys ought to be able to tell you what size you need for the new setup, and if they can't, I'd go for a different manufacturer.