How much FT/lbs to turn over SN2000

[tjmon1]

Hey you guys, I recently posted a weird boosting problem a while ago. I talked to Cliff at CUNDN racing and he said that if the boost falls off and then resets when i let it idle that there is not enough pressure on the balls. I told him that it is fairly easy to turn over the pulley by hand and there is no dead spots when rotating the pulley. The question I have is that how hard is it suppose to be? Cliff said 45 inch/lbs or so, that to me is not very much. That's equivalent to 4 ft/lbs. Can I just open it up and retorque the bolts? If so, how much do I torque them to? Someone help me out because I bought this unit rebuilt and it's kinda annoying. Also, I have never opened a SN2000, I have only dealt with a SN92.
Maybe the pulley is too small??? Any help would be appreciated,

Thanks,

TIm

[F=MA]

Pressure on the balls and races is controlled by the shim stack under the races, not the bolt torque. You can fine-tune it slightly with bolt torque on the case bolts. 45 inch/lbs is fine, this is a planetary design and that translates to hundreds of thousands of PSI at full chat. If boost is falling off, check the belt tension first. Mine makes 5 pounds boost at ~6000 rpm with the stock pulleys, on my E7 head Mustang.

F=MA

[tjmon1]

Thanks for the info FMA. How hard is it suppose to be turning the pulley over with one hand? To me it is very easy. So I take it that I will have to put shims under the race that is toward the impellar? I have tightened the tensioner and have replaced the belt. I do have about 3/4 of an inch left that I can push down on the idler pulley before it hits it's full tension limit. If I push the idler pulley all the way down to it's max, will that be too much pressure on the bearings? Do you guys think that going to a larger pulley will help? If so, does anyone have one larger than 3 3/8? Thanks for the help,

TIm

[F=MA]

45 inch/lbs is a stiff turn by hand. "Easy" is going to depend on how strong you are.

Re-shimming or rebuilding this blower is brain-dead easy. Do a search on here and you should find plenty of how-to info. Shims and parts are available from Paradise Wheels.

If you go to a larger pulley on the blower with no other changes, you are effectively stepping the blower down and you'll make less boost in normal engine operating ranges. I'm guessing you don't want to do that.

[tjmon1]

Well, I can't turn it with just my fingers but I can easily turn it with one hand. I have rebuilt a sn 92 (Didn't last long) before but not a sn2000. I have extra shims from my last blower. I won't be able to open it up until this Saturday, after that I will post and let everyone know how it went. This unit was "supposedly" rebuilt when I got it. It's just so weird how it will make boost until the motor gets some good RPM's going then just stop. Oh well, I will just have to put my nitrous kit back on until I get this fixed.

[tjmon1]

As far as the larger pulley goes, I was hoping it would have been just belt slippage. I tightened the belt and got another 1lb out of it, but the same old zero boost thing happened at higher rpm. No squealing, just S.O.L.

[pavement pounde]

First you need to know how much torque is needed to turn your pulley.

[tjmon1]

According to Cliff at CUNDN racing it's supposed to be 45 inch lbs.

[pavement pounde]

Yes, but have you measured that yourself yet with a torquewrench ?

[tjmon1]

I don't have an in/lb torque wrench only a ft/lb. I won't be able to tear into it today, maybe tonight though.

[F=MA]

A beam type inch/pound torque wrench is available from many part/tool suppliers for about 15 bucks and is a vital tool when working with the SN. clicker types don't work for testing rotational torque as the breakaway value clicks the wrench off.

If you want to try something before you take it apart, torque the case bolts to their max value (160 inch-lbs) and see if that helps. If not, you're into it to look and see. To paraphrase what I said before, a cross-eyed monkey could rebuild this blower.

F=MA

[tjmon1]

I am going to town today anyway so I will pick one up. As far as the sn2000 type blowers, the case bolts on the outside are just to hold the halves together. There is a set of bolts on the inside that need to be torqued to apply pressure to the balls. This is all according to cliff at CUNDN. That's why I said I have never taken apart one of these apart. I hear they are the same as the NOVI GSS blowers. I will give it a try here soon and see what happens. Hopefully it's a simple fix.

[pavement pounde]

There are no bolts inside, only the 4 that holds the balldrive bud that has nothing to do with the pressure on the bolts, you have either 5 case bolts on the front right next to the pulley or I believe 5 or 6 on the side close to the bracket.

[F=MA]

Trust me, you can tweak the pressure on the balls slightly the way I describe. What's the loss if it doesn't work? You have to then take it apart, something you were getting geared up for anyway.

F=MA

[pavement pounde]

What he says ^