About a year ago I purchased underdrive pulleys for my 3.1L. I never installed them becuase I always heard rumors of charging problems and such. Well it's come to the point that I want to get some more performance, and since I already bought them, they are sitting in my room, I want to put them on.

I heard just replacing the cranky pulley is better then doing both the crank and alt that the kit came with. The pulleys came with a piece of paper telling me which belt size I need for the two pulley setup. I did a search, and I didn't get any real results back, so that's why I'm here to post about this. Maybe I just don't put in the right words when I search or something...

But anyhow, I want to put the crank pulley only on my car and I don't know what length belt I will be needing. If any of you guys know the size or heck even the part number I would really appreciate it! Thanks a lot!

 

I don' t know the answer to your question but if no one else chimes in you could use a piece of string to see how long of belt you need. Just wrap the string all the way around, then take it off and measure. Parts stores should have just about any length.

 

the chrging problems could be due to not changing the alternator pulley. it has to be in the kit for a reason and im guessing(i could be wrong tho) that its there to avoid chargin problems

 

go to aspracing.com, they have a belt sizing chart on their site.

However, I have a crank only and got a .5" size smaller belt then they listed.

so says its 060755 (75.5") I got a 060750 (75.0") *size for reference only*

 

Thanks for the info!! May I ask what made you go for a smaller belt? Was it just for good measures? Thanks!!

 

The tensioner was almost to its outter limits when on, so I went that tad smaller. It "could" have gone full inch, but didnt want to push it.

So it was for "safe measure"

 

I had a charging problem with mine so i just used the crank pully email me if you need the belt size for your car what years is yours i hae a 91 with a 3.1 AC smog pump P/S and all that crap.

 

hey guys i still have my asp crank pully sitting in my garage and i never knew what lenght of belt to get. so on my 87 firebird with AC i need a 75.0" belt? if im only running the crank pully and i have AC and no smog pump.

 

Here is what you do. Take a string run it around all the pullys like the old belt was routed. Then measure how long the string is in inches. Then go to the store and say you need a belt this length in a K6 and there ya go.

 

or go to aspracing.com like I stated in my above post, look at their chart, then get a .5" smaller belt.

 

LOL! That's my attitude; take advice for what it's worth, and try it anyway. Either way, it winds up being proof (and a learning experience!) for some part of the yes/no argument! Let us know how it goes!

 

Don't worry about charging problems. As normal, if your Alt. is in good shape you will have no problems. I have both the crank and alt pully installed for the past 45,000 miles and not one problem. When I am at idle the charging drops a bit, but once I start doing 2MPH it goes back up to normal. BTW: this is with the radio, stero, high beams, and the dome light on.

The low charge at idle is by design. With both the crank and alt pully full charge doesn't happen till 11,00 RPM. How much time do you spend bellow 11,00RPM? If you drive like me the answer is, as little as possible!!