It did a make a difference for me just with the crank pulley. I think smoke_ur_5.0 had some before and after dyno # and the crank pulley alone is worth about 12 hp at the rear wheels.

 

I've done almost all the mods including the expensive ones like $1500 to CNC the heads, $500 Pro Mag rockers, $400 camshaft, etc. The pulley is well worth it based on a price/hp gain ratio comparison. The pulley is lighter in weight and smaller in diameter so not only does it allow your motor to spin up faster, but it turns your accessories a lot slower meaning they place less parasitic load on the motor. The factory pulley spins these devices faster than they need to spin so slowing them down a little doesn't hurt their operation. The only trade off is the alternator may not output 14 VDC at idle. Unless you sit at idle for extended periods at red lights at night with your heads light turned on BRIGHT with the A/C turned ON while you have your 1000 watt stero system cranked up full blast this should NOT be a problem. If it is you can just leave the OEM alternator pulley in place to keep your idle charge value closer to 14 VDC at idle. I'd recommend the pulley since it doesn't cost that much and is easy to install if you use a longer bolt to get the ASP pulley started on the crank snout.

 

Any clues on where to get a longer bolt? Each time I have changed them it has been a real pain to get the pulley seated so I can thread the bolt. I have had to Beat it with a mallet to get it to seat.

 

I had enough threads to start the pulley with the stock bolt. Then just hammered it on with a impact wrench! Works great!

 

If you have low charge at idle...just get an OVERdrive alt pulley (they are like $35 shipped, it is 1.75") and the $75 Delco 130A alt. That should be fine if you use the stock driven fan.

BUT if you have e-fans, pulleys, and want full idle charge...an investment in a 200A will be inorder. 1BADHD has a 200A unit.

 

I have the stk Alt. and E-fans with a 300watt amp. When I sit at a stoplight for a minute (at night) It drops a lil but my ? is if I get the pulley's (alt. included) will my volts stay the same or do I need to get the bigger Alt. Really don't want to change alt.

 

I was like that with the stock crank pulley and stock 105A alt but I have two big JL amps and with the A/C on in the summer my idle charge SUCKED. I went with the 130A and all is fine. I have full charge at idle with everything on...headlights, A/C, blower fan, e-fans, and stereo. I do have a cap in my stereo which should help too.

From my experience pulleys are bad on small charging systems when you hit them with a large load. I have a 130A alt on my F-150 with ASP pulleys and just picked up a 200A alt to go on with the electric fans I plan to install over Turkey Day break.

Honestly, I wouldn't even consider running underdrive pullies and e-fans with anything other than a 200A alt with the OD pulley. I want my blower fan to run full speed in the summer not halfassed due to low voltage.

 

So the my stock Alt will do for now, but I should look into 200A. The one on there now is a 120A. We are yall getting the Alt cheap.

 

GM has 105A and 130A stockers on the trucks. Unless you have a 6.0 with some snow package or the HO 6.0 you prolly have the 105A version. My 130A was from this RV place on ebay. Just search for "delco 130"

I think 1BADHD paid $250 for his? Maybe he'll chime in on this one.

 

What do the #'s on the side that 120A mean? On my sonoma it said 105A? I was thinking that was the amps, I could be WAY off. Thanks for all the great help here, by the way.