I have a 1991 5.0 engine. I would like to know what underdrive pulleys
> are. Will they give me increased performance? What things can I do to
> increase performance that dont cost alot? (like under $150) Any help
> will be appreciated.
>
> thanks in advance
> Evan
> 1966 mustang 5.0
They are larger diameter pulleys for your accessories, a/c, alternator etc. The theory is they turn the accessories slower and thus draw less HP. Some swear by them but unless you are racing at the track and trying to squeeze every last HP, my opinion is they are a waste of money. You may also encounter problems with the accessories not working properly, alternator not putting out enough current etc. Put the money into a set of 3:73 rear gears and you'll get a bigger boost in performance.