I have the opportunity to purchase underdrive pulleys that came off a 98 cobra for $35. I'm wondering if they will fit on my '97 4.6 F150. Also, is this actually worth doing? The only other change I've made is adding a K&N type intake.

Thanks

 

I'm not sure about the fit, but ud pulleys are'nt worth much in terms of seat of the pants performance gains.
Also, a two pulley set up will underdrive your alternator, which is usually ok, but didn't work well for me.
IMHO- save yer $. LOL

 

I woulnd't waste the money. I had underdrives on my 5.0, and took them off. They caused the engine to run hot, and the alternator to "underproduce" even with a higher amperage unit. I did leave the crank uinderdrive pulley on, but the rest came off. Save it for something else

 

Thanks for the replies. I appreciate all the advice I've gotten here, either directly or indirectly.

 

But I will add this. You live and you learn. What caused me and 20 other fellows issues may not cause you a single solitary problem. I would say get only the crank pulley and sell the others for best performance gains without losses in other dept's.

 

i've heard of many people putting on underdrive pullies and loving them. some say it's the best money they've ever spent. i bought a set myself a while back but changed my mind and decided to trade them on a set of 4.56 gears. for about $150 they seem like they might be a worth while mod to me. i heard of one person having charging problems from the small alternator pulley but that could have also been attributed to a bad alternator or battery too. i've also heard of a guy with a 5.4 with efans and the full set of pullies and no charging or cooling problems at all.

 

most but not all of the trucks use an 8 rib belt the cars all use 6 rib belts.. u could convert all of the pulleys on ur engine to accomodate but its best just to buy the ones for the F150. also the cobra uses a different water pump...

 

You can buy either 6 or 8 rib pullies from troyer. That is what I run, a small noticeable gain. Not worth the $150 or whatever they are new, I got mine used from the classifieds on here for like $75. Not too hard to install either.