Underdrive pullies and Wynjammer

[tunerpike]

Been sitting here looking at my supercharger and how it is set up and a question popped in my mind. Will underdrive pullies effect my boost? With this four pound kit I am guessing with my underdrive pullies I will be pushing about 2 pounds. Is anyone having this problem?

[flatblack]

thats a good idea....

[tunerpike]

Just read the thread on underdrive pullies and this sucks. I no longer have my factory pullies and putting supercharger on Friday.

[tunerpike]

My crank pulley is alot smaller then factory and the pulley that came with the supercharger takes the place of my alt. pulley and is bigger then factory. The supercharger is driven off the alt. pulley.

[ZR1-S10]

Ether get a stock pulley set from GM, or maybe you can call Al and he might be able to do something.

[nomaboy]

what engine???

[Maximus]

Hell junkyards are just over flowing with 4.3's.Go on the hunt for some used ones.

[tunerpike]

I have a 4.3

[tunerpike]

Just talked to a buddy that owns a junkyard and he has a 4.3 out of a van. Would that be the same dia. pulley as a s10 4.3?

[slowzq8]

you can easily calculate the size pulley you need, it is all just proportions. For simplicity sake, say you had a 10" pulley and a 2" pulley running on the same belt. If the 10" changed to a 5" the 2" would have to change to a 1" to maintain the same number of revolutions per minute. Just try to get a the right size pulley so your alternator runs as close to original speed as possible, or if it runs a little slow get a little smaller pulley for the supercharger. In your case maybe a 7 psi pulley will get you close to 4-5 psi.

[Supercharged-ZQ8]

Depending on how much smaller your crank pulley is, you're going to be losing a LOT of boost. Stock crank pulley diameter on a newer 4.3 is 7.5" -- which spins the impeller at about 38K rpm. If your crank pulley is 6.5" then your impeller will only spin around 33.5K rpm -- a definite loss in boost. I don't know how much smaller the underdrive pullies are than the stockers. Which year 4.3 are we talking? If you're dealing with a TBI kit, which is rated for 4 psi, then you'll have very little boost (1-2 at most at max rpm). If it's the SFI (rated for 6 psi), you'll see around 3 psi.

[tunerpike]

I have the tbi motor. My underdrive pulley is around a 5in dia., and on top of that, my pulley the came with the supercharger is about a 3in dia. Factory the alt. pulley is about 2in dia. I don't think it will even charge at a idle.