Hi, Mike I ordered and installed your 1715 and 4# pulley. I never measured it until today which means I am probably measuring it wrong ,"in the truck" edge to edge,.. what does your 4# pulley measure from edge to edge.. I measured approx. 8.10. Is this a 4#? I dont want to pull it off to measure Cir. *.31831.

I read a 4# pulley is 8.47, if I pull it off and measure Cir. *.31831 would I get 8.47?
....... are my dyno numbers consistant with a 4# and 1715 Its not possible that i got a 2#?

Similar 2# & chip dyno my numbers are about the same?

Do I need a Air Force One to keep up with my added boost?

thanks Clay

 

Hi Clay,

Nice to see you!

You're right, you can't measure edge to edge like that to compare - use an "outside" micrometer and measure it on the ribs where the belt actually rides. Also, you will find different numbers for diameters for 4 PSI pulleys - while most 6 PSI pulleys by now are pretty consistent at 9.0", and 8 PSI pulleys are pretty consistent at 9.75", the 4 PSI pulleys still vary a bit. There are also 3 different sizes of *upper* pulley from the factory on 1999-2003 Lightnings, ranging from a low of 2.93" to 3.0" to just over 3.0" - and that will also affect just how much boost you actually gain from the same size lower pulley.

The stock diameter of the lower pulley on the Lightning is 7.4" - and no, to answer your question, you could not possibly have gotten a 2 PSI lower pulley from us, as we don't even sell them. In fact, I haven't even seen a 2 PSI lower pulley (which would be 7.8" by the way) in about 3 years.

You will not know what your "dyno numbers" are until you actually go to a dyno - and I wouldn't worry too much about dyno numbers, or trying to compare what your vehicle might do as compared to some other vehicle in a 2 year old post out on the Internet as in that link you provided. Many of the numbers are from Dynojets, which tend to read 15-35 HP higher than say, a Mustang dyno for example, and so on - it also varies from one vehicle to the next, and varies according to atmospheric data - big time. Dynos are not some mythically accurate machine or device, they vary - so their data isn't absolute, it's relative. We never try to compare different vehicles or even the same vehicle run on different dynos, etc. A dyno pull on a chassis dyno is just an approximation of power at that time, on that machine, with that operator - for us a chassis dyno is just one form of tuning platform. Just because you register say, 400 HP at the wheels on one dyno pull doesn't mean that you will make that same power number again - it might be higher or lower next time, with *no* changes to the vehicle.

Sure, it's always nice to have some dyno numbers, but what really matters is the actual performance of the vehicle - at the track and on the street. Heck, just changing the TQ for a 2600 PI unit like I run will drop a bit of HP on the dyno, but still reduces ET's by 2-4 tenths.

With regard to your question about do you need an AF1 to keep up with the increased airflow, this depends on what your current intake setup is - if it's still stock, then yes, I would advise putting an AF1 on there as you're leaving 20 HP SAE on the table using the stock factory intake with a raised boost pulley. Any time you raise boost, yes, you should reduce restriction in the air intake tract - that will give you more boost gain thus more power, and allow much better breathing with an end result of about a 20 HP gains SAE over a stock intake with the pulley.

I hope that info helps, & feel free to give me a call to go over any of this or anything else performance related about your truck!

 

I measured my stock pulley (O.D. of the belt surface on top of grooves mulitiplied by .31831) and I got 7.430...... I just removed the belt on the pulley you sent me and measuring the same I got 7.925. I can bring a large dial Caliper home from work Monday, but my measurements are accurate enough to know the pulley is under 8" .... is this what you measure on what you have in stock ??, according to searches on pulley size its a 2# ?


from what I read ,

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

and RPMOutlet lists the sizes like this:

+4 pulley ... 8.47"
+6 pulley ... 9.00"
+8 pulley ... 10.00"



Mike, I have before and after dyno numbers in my sig. ?
and an after mods video of my dyno pull in my sig.
I am being told that 386/465 is consistant with a chip and a 2#pulley? anyway I'll try to call you Monday........



thanks Clay

 

ttt Mike thanks for taking care of this supplier problem. New dyno numbers to come with a 4# and Air Force One.

 

Hi Clay,

Wow, what a story, eh? I just love getting egg on my face - just as soon as I say I'm sure there's no way, it turned out that our manufacturer did in fact make a mistake and sent us the wrong part#. So you were right!

In speaking with you before, I knew that we had not even *seen* a 2 or 3 PSI pulley in about 3 years or so, but as we talked more & more on the phone, the numbers just weren't quite right even with the amount of variance we see in the 4# units from various manufacturers - and what you have there is more like a 2.5-3 PSI pulley, and is rated as a 3 PSI pulley.

Thanks for waiting on the phone while I went to the stock room and opened up several of those units to measure them right then & there, as we found the exact same measurement you found - BINGO - there's the other 6-8 HP!

Luckily, only 1 other person got one of those pulleys from us, and we're contacting them to let them know - it was a simple supplier mistake and easy to correct - but thanks for staying on top of that & working with us Clay, it's greatly appreciated!