Redchevy808

Ohk I know an underdrive crank pulley is smaller than stock which slows down my serpentine belt and puts less load on the motor. I've been looking at threads saying charging and cooling are messed up, but why would they if the kits come with smaller than stock water pump and alternator pulleys which will spin their respective devices faster than the stock ones? Or are these people only installing a crank pulley? I need some facts here

eseibel67

The OE pullies were designed so all accessories will work together for a long time. Changing anything will come with some compromises. A smaller driving (crank) pulley will slow everything down. A larger driven (everything else) pulley will also slow down whatever component it's installed on. This is how underdrive pullies work. If a smaller pulley is needed to speed up a water pump, it's sort of defeating the purpose except that other components will be running relatively slower. I wouldn't bother with any of that at all, I used them on a 305 TPI 20 years ago, and I found the gains were minimal. I think they are popular because they can be easily installed with the tool set your mother has in the kitchen.

pound

iTrader: (7)

The reason why the kits include smaller water and charging pulleys is because you don't want to slow some parts down as much as others. For example lets say you buy a pulley kit and the smaller crank pulley will slow everything down by 50% (making that number up). Well your smog, and power steering might be ok with being slowed down 50%, but the water pump and alternator might not work so well. So you solve that by putting smaller pulleys on those parts to speed them back up a little bit, but not quite back up to stock speed. Using the different pulley sizes like that will let you slow down some accessories more than others.

cuisinartvette

Have a pretty expensive underdrive kit...nice but wouldnt waste money doing it again. Yes alt may have to spin more to charge properly and everything else youve read. My mistake has me trickle charging my batt all the time now get to spend close to 500 for a better alt and bracket then the pain of making it all line up again. shoulda bought a march kit of stock and left it the hell alone.
Do a real mod where you can see some gain for the money spent.

rick.meza

Can I get some help figuring out what the pulley under the a/c compressor is? Its the only pulley that doesnt spin freely and the cap or wheel came off. On my 92 camaro 305 tbi

eseibel67

It's the A.I.R. pump. There's not too much inside those things, I'm surprised it siezed. If you remove it you might be able to free it up on the bench.