I recently bought an ASP replacement underdrive balancer since I needed a new one so I decided to try it. Well I don't like the way it charges now so what overdrive alternator pulley will put me back to stock charging. Also what belt will I need?

 

i have been running an underdrive pulley only for 5-6 years with no problems. I also had a big stereo in my car for a long time and the altenator charged with no problems.

 

well mine does too unless I'm stopped in traffic with heat and lights on then the voltage drops in the red which is what I don't like. I've been looking at ASP website and it appears that the overdrive alternator pulleys are smaller than the stock pulley, so now I'm confused. Do you need a smaller or larger pulley to bring voltage back up.

 

Since your crank pulley is smaller, you also need a smaller pulley for the alternator to bring the RPMs of the alternator back up. It might not be exactly the same as stock, you would have to know the diameters of the alt pulley and the crank pulley, both stock and under driven to figure that out.

I personally don’t see a reason for an under drive pulley for an LT1 car; all you are actually under driving is the power steering pump. The A/C compressor can be turned off and the water pump is mechanically driven, and since you are contemplating bringing the alternator back up to factory spec, you aren’t gaining that much, are you?

 

yeah your right that the gain ain't much, but like I said I needed a new balancer anyway and thought I'd give it a try after all it is lighter than the stock unit anyway.

 

MBA has a pulley that will overdrive the alternator 10%

 

ASP has an overdrive pulley that is 1-3/4" part number is ASP520004
says its for 84-96 4.3, 305,350, and 454 engines. Would this work for the LT1? If so what belt would I need?

 

I have a underdrive crank pulley also, I did not like the voltage I was getting when at idle so I went to a local alt/starter repair shop and got a smaller alt pulley it was $6 ,I got the smallest they had, it helped + I ran a bigger ( 4 awg) wire from the alt to the batt, the stock belt is 64 in I got a 60 in with the u/d pulley , but next time I get a new belt I will get a 59 or a 58 in