So I did a google search and found a couple of older threads. My question is is it worth it to so the under drive pulleys? Also I did find a thread a while ago about using matco pulleys. Just wanted to see if anyone can provide newer info about doing pulleys. I own a 07 f150 with the 5.4.

 

I remember somebody telling me that it was not worth it if you have any sort of load that needs the alt ... I have a lot of emergency lights hooked up on my truck

I'm sure somebody with more knowledge will chime in

 

I had underdrive pulley on my '01. I liked it to be honest, but I also had a little 4.6, 2v then as well, so it needed all the help it could get. I didn't really have any charging issues. I had my Sirius radio back then and had boat or camper hooked up without issue. I intend to get one for my current truck at some point.

 

Free advice so value it compared to cost. I would not recommend underdrive pulleys if you tow or off-road.

I tried underdrive pulleys on my old 86 Monte Carlo SS 305 V8 way back. I estimate it freed up about 5 hp. (advertised up to 15hp) If you have a 7,000 rpm engine, of course if frees up more, maybe 15. On that car, the alternator voltage was a little low if the AC blower was on or the head lights were on at idle. I found no difference in the power steering or cooling although I was careful about heavy city traffic.