Crank Pulley Size

[Tonka Toy]

I bought a used JLP pulley from a local guy that upgraded his pulley. He told me that it was a 4lber. I read somewhere in a thread that most 4lb pulleys measure 8.5inches. Well, the one he gave me measured 9 inches. When I got my truck dyno tuned the other day, with the pulley on it only increased 29hp/45lbft. That sounds like a 4lb pulley to me. What do you guys think? Did I get a 4lb JLP pulley or do you think I lucked up and got a 6 lb? If I did get the 6lber why didn't I get more hp/torque out of it?

Thanks,
Dave

 

[Tonka Toy]

Anybody?

 

[SVTJAY]

my 4lbs lower is 8.5"

stock is 7.5"
2lb is 8"
4lb is 8.5"
6lbs is 9”
8lbs is 9.5”

 

[Tonka Toy]

Where did you measure the pulley from?

 

[Blown347Hatch]

Originally posted by LTNG FST
Where did you measure the pulley from?

Center of the lip on each side straight through the center.

 

[Tonka Toy]

Center of the lip? I just put the tape measure over the edge. Here is an example of what I mean. Just used an upper pulley as an example of where I measured from.

 

[2bscrewed]

I got my 9" from KB which most people say is a 6#'r but they are very attament about not calling them that. Especially since it changes with their and other blowers. They only go by ratio's.

 

[Tonka Toy]

So what does KB call a 9" pulley?

 

[2bscrewed]

A 9" crank pulley. Or "cool crank pulley" Since it's vented and weighed less than the 3" supercharger pulley.

 

[TXRickC]

Like pictured above, that may give you close to 9" cause your measuring the outer lip, you need to measure from the crest of one of the ribs/grooves.

 

[Jkstang78]

here are some lower pulley diameters I found from a search:


2# = 7.90"
3# = 8.17"
4# = 8.50"
5# = 8.75"
6# = 9.00"

 

[Tonka Toy]

Originally posted by TXSVTLIGHTNING
Like pictured above, that may give you close to 9" cause your measuring the outer lip, you need to measure from the crest of one of the ribs/grooves.

This is where I think I am measuring wrong. I looked at a 6lb pulley at FFW in Richmond on Saturday and it looked bigger compared to mine. So, I'm sure it is a 4lb'er.

Thanks for all the info!

 

[Albuquerque ALI]

need more info

 

[bmfgsxr]

you need to measure from where the belt makes contact to the pulley. not from outer lip to outer lip..

 

[Thunder Bolt]

you need to measure from where the belt makes contact to the pulley. not from outer lip to outer lip..

That's it. :thumbsup: My 8# pulley measures out at 10"