Pleae Help underdrive crank pully alternator not charging

[cinz4064]

i recently installed a underdrive crank pully in my mark viii now the alternator isn't charging at an idle that pully is still stock do i need a bigger or smaller pully for the alternator
also if i change the idle whats the max rpm i can set it to without messing anything up

 

[topher5150]

you can get a three piece pulley kit with bigger pullies for the alternator and the water pump to help compensate for the size difference in the crank pulley

 

[racecougar]

The bigger pullies for the alternator and water pump slow those accessories down even further. If the OP wants to speed his alternator up, he/she needs a smaller alternator pulley.

 

[keatonsdad]

Then doesn't that defeat the idea of the under drive crank pulley?

 

[cinz4064]

the kit came with a set of 3 pulleys and the alternator pulley is the same size as the one on my alternator do you know where i can find a smaller pulley for my alternator

 

[danny_holtermann]

ebay... also you didnt change nything internally on your motor so don't go up in rpm

 

[racecougar]

Then doesn't that defeat the idea of the under drive crank pulley?

Yep. On the alternator at least.

 

[driller]

Look here for a smaller pulley... http://rjminjectiontech.com/collections/alternator-accessories/products/pulley-6rib

You still will benefit from the underdrive crank pulley.

 

[chris2523]

Look here for a smaller pulley... http://rjminjectiontech.com/collections/alternator-accessories/products/pulley-6rib

You still will benefit from the underdrive crank pulley.

whats the stock alternator pulley size?

 

[driller]

whats the stock alternator pulley size?

2-3/8" diameter

Caveat - if you use the 1-7/8" diameter pulley and hit the rev limiter often, you will stand a chance of over-revving the alternator. I know I did a couple times.

 

[JC1994]

had motorsport ud pulleys on my Mustang you could tell the HP gain but driving around town even with 373's I had to put it on the battery charger after a night of cruising. did ok on hiway trips.