I just picked up a 2000 5.3 rcsb with a tvs1900. It came with 2 pullies. The one out of it has 3.6 written on it and when i put the calipers on it on the outside lip i get 3.7. Measuring of the one on the truck the same way i get 3.4. Would it be safe to assume its a 3.3? I get 7-7.5# out of it.

 

I just measured the pulley on my whipple this weekend and putting the calipers on the top of the ribs seemed to give me a measurement within a couple thou. Using the lip will give you a bigger diameter as you are seeing. Try to measure the peaks of the ribs.

 

How you measure doesn't really matter. What matters is that you measure both the blower and the crank pulley the same way to calculate a ratio. You may have a 6" crank and a 3" blower.........but when you measure it, it comes out to a 12" crank and a 6" blower..........ratio is the same.

Like I said, measure both pulleys the same way and you'll be good to go.

 

Very valid point. Only reason it may matter is if you're trying to get a rough approximation of how many more pounds of boost you'll get by switching from one pulley to the other by using the 1/8"=1lb rule of thumb. I would use Atomic's spreadsheet to do this more accurately though.

 

Its just the stock crank pulley. Im just trying to figure out what the actual size is of the one on the blower. Theres no part number on it. All i know is i got 3/10" difference between the 2.

 

I would say the one with 3.4 stamped on it is 3.4 and the one with 3.6 on it is 3.6...

 

Neither are stamped with anything. The bigger of the 2 has 3.6 written in sharpie. The other has nothing. The bigger one measured 3.7 on the outside lip and the smaller measured 3.4. Im going to assume 3.6 and 3.3 hopefully trusting the sharpie but cant be guarnteed.

 

I would feel more comfortable measuring the ribs as opposed to the lip. The belt doesn't ride on the lip...

 

That's how I got within 0.002" of the size engraved on my blower pulley, measuring the peaks of the ribs.

 

Oh, ok, I thought you said stamped. The pullies I have used in the past always have the size engraved on them.

Measure from the tips of the ribs (not the outer lip).