ok im just wondering do underdrive pulleys actually increase your gas mileage at all? also would one cause any type of towing problems? electrical wise?

 

I don't know about the mileage. It may increas a little, but I wouldn't expect more than 1 or 2 mpg. As far as towing I can't see why it would cause any problems and it is ussually a good idea to get the overdrive pulley for the alt so the electrical system will work properly at idle.

 

honestly at 2mpg increase it would pay for itself pretty quick with the amount of driving i do. what is a good one to get?

 

I would look into ASP Pulleys or go to rpmoutlet.com and get the motoblue set for $250 bones. My bud in Michigan put a set on his 93' c/k and noticed a difference in towing and under hard accelaration. I will be getting a set for mine soon. Be sure to get a good belt too. Goodyears gatorback is a great one. Just remember, you get what you pay for so do some research. When you get one installed tell me if you noticed anything?

 

ASP makes very nice pulleys. They are worth every penny, but I wouldn't expect to see a noticible MPG gain.

 

My gas mileage got a little bit better with an ASP pulley & electric fans. My switch from 3.42s to 3.90s gave me 1-2 mpg in the city btw.

 

What about performance gain? are they worth the $ and does anyone have a pre/post dyno sheet?

 

If you go with an underdrive crank pulley I suggest also getting an overdrive alternator pulley. That is my suggestion from experience.

 

I gained 16rwhp/6rwtq from electric fans/ASP Crank Pulley. No alternator pulley here, no problems so far.

 

I don't have a dyno sheet but I had a ASP underdrive on my truck and it was more responsive. When I removed it I noticed the throttle response decreased a bit. Also when I took it off I lost probably 1/2 mpg. I didn't do the overdrive alt pulley and the truck has the factory HO alternator 160amp or something like that. Anyway with the 6HI conversion at idle I would only drop 1/2 a volt and the lights wouldn't dim at all.