Underpulleys

[muzzy1maniac]

Has/Does anyone use these? What are the +/_ 's and are they tough to install?

[wolfox]

Undercranking pulleys are used in order to reduce accessory drag on the engine, and reduce weight on the crank. Every pound you shave off is like getting 4 horses at the crank back. This is achieved by swapping your steel pulley for an aluminum alloy pulley, and of course, it's slightly undersized. You'll get one for your A/C and alternator pulley too. (NEVER undercrank your power steering) It's a poor man's boost if you get a whole and complete undercranking kit, maybe at best scavanging back about 12 horses at the most from our trucks. The only downsides I can think of are 2:

1) I live in a pretty swampy climate in the summer. I don't want to get damp and lukewarm when sitting idle in traffic with my A/C running at less than optimal RPMs.

2) You increase demand on your battery as your alternator will be turning at a slower rate, especially at idle. If you are running heavy accessories, or running windshield and back glass deforsters, your wipers and lights in the rain, you will dip well below 12 volts on these trucks. (With the undercrank pulleys) You need stable 12v~13.8v to keep things like your computer and tranny control modules happy and your transfer case actuator motors sliding smoothly too.

You will also have to size down your serpentine belt to get everthing snug and spinning right again. Your old belt will be more than oversize and will cause stuff to squeak or really run erratically until you got the next smaller size belt into place. Other than that, well, you decide. I personally wouldn't do it.

[muzzy1maniac]

Thanks - I appreciate the input. Seems like too much work and $$ for too little gain.

[dmbrisket 51]

it is alwase a lot of $$ when your talken hp gains, especeally the ones that seam worth it, ie a blower... underpullys are good if you want to squeeze that last little bit out of your moter, for a daily, i wouldnt reccomend under drive pullys in a full kit, maby one on the ac, and alt, but not the crank pully.

[01shavedblaze]

I have to agree, they are not good for an everyday driver. Especially if you do alot of in city driving. I just took mine off and put the originals back on. I have an 01 blazer xtreme and it was overheating with the a/c on in traffic and I went through 2 batteries before I decided to take them off. With the underdrive pulleys, even with original alternator pulley, my voltage was dropping almost to the red when I was at a stop or in traffic. I also have flexalite electric cooling fans and they couldn't keep her cool enough in traffic. I took them off about a month ago and haven't had any overheating issues or battery problems. I wouldn't recomend them, the power increase isn't worth the headache.