Poor mans alt. under drive pulley

[Southern3.0]

I have a few boxes of stock 03/ 04 Cobra parts in my garage and I was digging around in them and I founds some pulleys. I was looking at them and the stock alt. pulley looked just like the alt pulley on a ranger but a little bigger (fatter too cus its and 8 rib pulley) and I got to thinking, looked at my stock alt pulley and said "what the hell its worth a shot". Sure enough it fit on my alt. and the belt still lined up. I didn't notice any diffrance in performance and my headlights are dimmer at Idle so I'm probably gonna switch it back but if anyone is thinking about under drive pulleys a Cobra alt pulley is bigger and fits.

 

[dude772]

i did the same thing when i did a poor mans rebuild on my alt on my 90 4.0L.
I used the alt. from an 86 grand marquis with a 351 and the front case from the ranger, bolted those together with good looking brushes and the smaller pulley of 3 alt i had, not sure what the third was but the pulley was definitly diferent.

so i got what was proably a higher output alt. with an under drive pully, plus a shorter belt, but it needed 1 anyway

 

[AgPete139]

Your accessories are just turning at a slower speed, and you are not really going to notice a difference in power. You usually just reduce the size of the crank pulley, and the whole system that the belt touches is all ratio-related. It "frees" up power by driving all the external accessories slower (A/C, alt., idler, etc.). Less turning mass for the crank as well...

Sell those parts you currently have a buy a real underdrive pulley from someplace like Underdog. $156 new, and it will give your 3.sl0w something it can actually use.

 

[MAKG]

Power is not just the speed at which one turns the accessories. It's the speed times the torque. A regulated system will raise the torque needed by precisely the same factor the speed has been lowered.

For regulated systems like the air conditioner, power steering, and alternator, expect little or nothing. They will draw the POWER they need to drive the accessories, whatever that might be, until you max out the regulation. IF you max out the regulation, congratulations, you just made a POS. You might make the water pump a little slower, but that's hardly a good risk.

 

[blackbronc]

Hey DUDE772, a smaller pulley on the alternator will overdrive the unit. you may want to try the biggest pulley to underdrive. What you have set up now is going to produce more amps at lower rpm. sounds like you don't have a horsepower shortage so the extra amps will help run that 150 db. stereo, driving lights neons DVDs whatever. If you put the big pulley on you may see a discharge at idle speeds. It's fun to experiment.

 

[dude772]

Hey DUDE772, a smaller pulley on the alternator will overdrive the unit. you may want to try the biggest pulley to underdrive. What you have set up now is going to produce more amps at lower rpm. sounds like you don't have a horsepower shortage so the extra amps will help run that 150 db. stereo, driving lights neons DVDs whatever. If you put the big pulley on you may see a discharge at idle speeds. It's fun to experiment.

oops i read the underdrive thing wrong haha yea thats what i was aiming for. DERR!! haha I had a stock 4.0L at that time and i wanted the extra power because of the stereo and lights and ac all running at the same time. Never had dimming headlights after i did all that alt. mod stuff.

It was a high output, high velocity alt.