MOhecan

i jus installed the underdrive pulley for my 91 mustang. i didnt install the alternator pulley cause alot of people on here said not too. but the factory belt is to big. what size belt do i need?????

mattdel

which one(s) did you use

MOhecan

water pump and crankshaft they are bbk underdrive pulleys

mattdel

what part number is on the box

MOhecan

1513

notch5oh

are u replacing the belt at the same time? i did when i did my pullies and the factory replacement belt i got was too big, someone told my a/c compressor had been replaced with a newer style at some point and it took the next size down

i doubt thats your problem but i thought i'd throw it out there

mattdel

according to the install instructions the stock belt fits.

2 kwik

it does when you use the alt pulley..

MOhecan

i havent repalaced the ac. but when u go to get the belt u have w/o air, factory air and dealer air. i tried factory and i think w/o and the dealer air belt is inbewtween them in sizes. so i think i might try that. but i was right not to put the alternator pulley on right?

mattdel

The BBK Street Pulley Kit is designed to increase power by reducing the overall speed of the serpentine
system, and should in no way create a charging or cooling problem. However, an examination of
the fan clutch, thermostat, and radiator should be performed to insure proper operation. (Cars
equipped with high drawing aftermarket sound systems should check charging effectiveness before
installation of underdrive pulleys.)