I have been trying to decide what to do about my battery charging issue. I have a 97 z28 and think i have an underdrive pulley. I know I have a shorter belt than the stock belt b/c i tryed to change it out when i needed a new one. my pulley looks like a smaller pulley with a bigger one bolted to the outside of it. All the pics I look at seem to show just a single pulley. I was going to buy a stock sized pulley to see if that was my problem was looking for any info anyone may have before i waste money or time...Thank You

 

My stock pulley/damper is 7.5" across if that helps you any.

 

Sounds like you may have a "sandwich" type underdrive crank pulley. Bolts between the stock damper/pulley and the crank hub.

 

On my truck as long as im above 1500rpm I get enough charge. Your volt guage should help you see. Watch it to see when ur below 13 or whatever as well as when you climb above. If your driving stays on average above that range you probably have a problem elsewere and may not be worth swapping. If your at idle alot might be good to switch. Sounds like some people struggle with getting some of the underdruve pulleys off so might keep that in mind.

 

Another thought I dont know if is applicable but putting a smaller pulley on alternator would kick it up too

 

Well, that's true but wouldn't it just be easier to remove the crank pulley?

Really, on these cars, because the water pump is cam driven, the advantage achieved by an undrive setup is pretty minimal.....

 

Agreed. Just remove the underdrive pulley.

 

.I agree not much gains with underdriving this motor (and thats exactly why i am not familiar with the underdriven pulleys and possibilities)but my comment was based upon other posts ive ran across with others attempting to remove underdriven pulleys that fused as they put it or rusted together and never heard if and or how they had success removing it and what if any damage to the hub or pulley. My point is if he doesnt have luck getting it apart there could possibly be another route to spin the alternator faster. I just dont know whats available pulley wise but on my truck setup they did give the smaller pulley for the alternator. If he couldn't get them apart in my opinion it would be worth checking into before beating too hard to bust it loose or taking it to a shop. My point is what if they make that pulley and its less than twenty bucks which I doubt anyone offers but who knows

 

Sure, we understand that...but it can come apart if the person works at it. Rust can be overcome and a puller can be used to pop off the balancer...

 

So you dont need the smaller pully?? im confused

 

No, you don't need a smaller pulley. The poster that mentioned that suggested it as a work around in case the pulley is rusted onto the crankshaft. Certainly valid but reallynot necessary if you can get the balancer off the hub. And, of course you can...it's just a matter of how hard you have to try.

All you need to do is raise the car, remove the belt. Remove the three bolts holding the balancer to the crankshaft. Spray the hub area liberally with a penetrating oil like PB blaster....WD-40 is too light duty. After soaking a while, try to remove the balancer by pulling it off the hub. If it doesn't come off, use a three armed puller through the holes in the balancer, NOT on the outside rim. Do NOT use a hammer. If you do either you will likely ruin the balancer. After you get the balancer off remove the aftermarket underdrive pulley...it maybe rusted together. Put it all back together like you took it apart.....