I have a set of underdrive pullies going on a 6.0 swap motor. I am wanting to put some fans on it. The availaility of LS1 fans are forcing me to look at Flex-a-lites.

Will there be problems with fans that pull 28 amps when there are underdrive pullies on the crank and alternator? There are no other loads on the electrical system, everything is stock. Well, I will be adding a tach.

 

I'm not certain myself but i'd assume you could either go with a larger pulley on the alternator or just get a new alt. with more amps.
But as i said, that's just an assumption.

Thats if you have any problems at all.

 

I'm running underdrive pullies with overdrive alt pulley and no stereo system my voltage drops to about 12.5 while at idle with ac and lights on, fans at 100%. I'm going to a 130 alt to play it safe once I install my stereo.

 

I got the high output alt from the factory 145 or 160 amp, and with the underdrive pulley, stock alt pulley and the 6hi conversion my lights would BARELY dim at idle the the volts would only drop a half a volt.

I would recommend a bigger alternator and maybe a optima yellow top if your afraid the battery would cycle a lot.