What size pulley are you guys running on the blower? I called to order a smaller one today and they told me I already have the smallest one they make! I am running a 3 1/8 but it came with a 3 5/8. The stock pulley made about 5lbs on the 5.3 so I changed to a 3 3/8 and went to 7 lbs. Then I bought this 3 1/8 and was nudging 10. When I put in the 6 liter it fell off to about 7. I am wanting to get it back up to around 10 with the 6ltr but if they don't make a pulley, what do I do?

 

Part of the problem is even though you are only seeing 7lbs now you are still spinning the blower just as fast as you were when you had 10lbs. Maybe you are getting to the limit that your unit can be spun safely and/or to make efficient boost?

Some blowers can be spun beyond their normal efficiency but you hit diminishing returns in actual CFM and the extra heat generated. Could this be why they dont make a smaller pulley?

If this isnt the case then I'm sure you could have a machine shop or a place like March cut you a new pulley. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

 

You can get a larger crank pulley. My kit had a small crank pulley and my blower pulley was a 3 1/8. This gave me 7 psi on a 5.3L. Most guys with bigger crank pulleys will have 4"+ compressor pulleys.

Ask around on some boards for a used pulley. I hate paying Whipple $60+ for each pulley. They are making a killing.

 

i have a 2 1/2" pully siting right here, it gave me 11+ psi with the 6.0.

the answer i got most from whipple was 15000rpm is the highest we should go(got diferent answers every time), he wouldn't elaborate on that at all. my question was is that for a boat or soemthing that might be spining at that rpm for 30minutes at a time or for a truck that might only see that for a sec or so and he wouldn't say.

you probably have the 6 1/4"pully like me so with a pully like the 2.5" that i have the blower would be at 6.25/2.5x6000rpm = 15000rpm. looks to me like you can push 11+psi without exceding the max rpm of the blower. prety sure they make a 2 3/8" pully too. check out my original and the 2.5" unit, i get them for $45 now for being a frequent buyer.

<img src="http://members.aol.com/cobra99vert/images/dscn1005a.jpg" alt=" - " />

<small>[ April 21, 2003, 10:36 PM: Message edited by: parish8 ]</small>

 

My Whipple kit came with the 4 1/4" pulley and it was making 6 pounds of boost. Why does it seem that every kit has a different size pulley on it?

Kent

 

I just measured my Whipple pulley. 4-1/4 also. I see a max of 6 lbs. with headers, cam (with 112.6 lsa i.e. too much overlap for a blower that is making it vent some boost) and exhaust.

So one should probably see 2 lbs increase for every 1/4'' reduction in pulley size? as per L-EATER's experience of pulley swaps?

 

1999stepside,
I believe the reason why some kits have different pulley sizes for the same engine is that they improved the way the supercharger belt is mounted. Mine is the older kit that has a seperate belt for the supercharger & yours is the newer kit that has supercharger belt tied in with the factory serpetine belt. The problem I had with my belt configuration is the extra supercharger crank pulley kept working its way loose & I had to replace my harmonic balancer & pulley to get it to stay on.

 

That pisses me off! Why would they tell me that 3 1/8 is the smallest they make? (they also said that the only crank pulley is a 6 1/4) I have a friend who is good friends with the owner of a local machine shop and he is taking one of mine in today to let the machinist look at it to see if he can carve me one out. Theres more than one way to skin a Whipple......

 

After calling Whipple 3 times and talking to 3 different people I finally have a pulley on the way. All 3 first told me they don't make anything smaller than 3 1/8 (after I told them that is what I already had) The third guy says "we don't reccommend running more than 6 psi" and "We don't make anything smaller than 3 1/8" I say why? and he says because you would run into detonation problems. I told him that I could tune around detonation and he says "just how would you go about that?" I say I have a program on my laptop that I can adjust the timing and fuel with and that I have some bigger injectors on the way. He then immediately says "what address would you like the pulley shipped to?" What a bunch of idiots!! Anyways I am getting the 2 3/4 and it is supposed to be here tomorrow.

 

i am not sure why they would give you the run around like that but my experience is that he is right about the 6psi limit. you can pull timing and run rich but i doubt you will get away with that 10psi pully without some good gas in there, like 100octane or better. i think 7psi would be hard to tune for with pump gas.

good luck with your tuning and where is that atap file?