SN 2000 Disassembely and inspection, help/info needed...

**444** · 11-27-2009, 04:42 PM

Hi there everyone, I'm new to the board and about a year ago I purchased a used paxton sn2000 supercharger. The previous owner of the supercharger claimed he put a rebuild kit in it to the tune of $450, but when he sold it to me he included all the used parts in boxes. After comparing the parts to the rebuild and refresh kits I see available for these superchargers, it looks to me more like he put in a $120 refresh kit.

Instead of just installing the unit and praying it works, I figured it would be a good idea to disassemble and inspect the unit. However when I purchased this unit, I did not realize how hush-hush the tech info on these things really is.

So I plan to take it apart and do an inspection. Take some pics, post them, etc. What are the main areas of concern I should be scrutinizing? From what I've read, the ball drive, shafts and the clearance/tension between the balls and their race seems to be the biggest issue? Previous owner told me that cundForgive me, I am a newbie when it comes to these paxtons so any helpful tips or info you guys can provide would be great. I plan to tear into it this weekend. Also while I have the case apart, I figured this would be the best time to drill the case for an external oil cooling system.

I did contact Craig at Paradise Wheels at one point and he informed me the drag on the front shaft should be 22-25 inch lbs at 15rpm. That's about the only real piece of tech info I have on these units.

I'll start tearing into it saturday and post some pics of what I've all got. Thanks everyone for your help and I look forward to hearing from you.

**JPJP** · 11-29-2009, 12:16 AM

Craig gave me a value of 20-22 in-lbs with no seals and add 5-8 more with seals installed (25-30 in-lbs) with no RPM specified. ..maybe because mine is a SN 89.

I recommend you just turn it over by hand and if it turns freely with little to no notchiness try running it. You will probably get a few seasons of running out of it.

**Michael** · 11-29-2009, 11:09 AM

Hi 444, welcome to SCH.

Assuming you haven't done so already I would highly suggest you perform a few searches on this site for the disassembly and reassembly information you'll need prior to getting started. I am quite sure you'll find a lot of useful tech info here.

I would also consider asking the previous owner of the supercharger what rebuild kit he used and where he purchased it from prior to opening it up. As you've implied, there are varying degrees of rebuild kits, some with more replacement parts than others. If the previous owner purchased the rebuild kit from Paradise Wheels for $450 I would bet it was more than just a simple "refresh kit"... maybe he upgraded the impeller too? That's $200 alone, I believe. If he got the kit from some other supplier, then it's not unreasonable to think that he may have just overpaid for a "refresh kit".

If you can spin the supercharger and don't feel any binding or notching, then chances are good the internals are fine; place a torque wrench on the input end to check whether the drag is between the 22-25in-lbs mentioned by Craig. If that's the case, then I don't think you have anything to worry about.

If, however, you have opened the unit up already, the kinds of things to look for are obvious wear on the drive balls and races. You'll also want to check the clearance between the impeller and backplate too (according to our resident SN expert speedytang, the tighter that clearance is, the more boost you'll build). Take some photos and post them here - that will make it much easier to help.

**444** · 11-29-2009, 02:32 PM

Thanks for the help so far guys. I popped the covers off and took some pics. Hopefully you guys can tell me I'm not missing any parts. Like I said, the previous owner claimed he bought a 450$ rebuild kit, but when he sold it to me he said he would include all the used parts he swapped out. You can see in the pic the used parts are a couple bearings and seals and a set of new balls. I think that's just the refresh kit, right? He said he bought the kit from cund racing off that auction site. One of the old bearings feels pretty notchy so I'm guessing that's why he tore into the unit and replaced parts. But now it does turn over smoothly by hand, no notchy feeling.

Here's a pic of the unit plus the used parts that came with it.

Everything's very clean in here, previous owner did a nice job of cleaning it when he took it apart to do the kit.

**444** · 11-29-2009, 02:34 PM

Here's a pic of the implellor. Does this look like a stock impellor or a HO impellor. Cund racing has pics of both on their ebay site, and to me the curved fins look more like a HO impellor, or is this the impellor the sn2000's came with stock? Clearance between the impellor and the housing looks to be very tight, although I did not think to stick a feeler gauge in there.

Stock impellor from cund:
http://cgi.ebay.com/ebaymotors/Paxto...Q5fAccessories

HO impellor from cund:
http://cgi.ebay.com/ebaymotors/High-...Q5fAccessories

**444** · 11-29-2009, 02:37 PM

Back cover here, looks normal to me..?

Oil pump housing and ball carrier look good to me from what I can see. Did not notice any wear on them.

**444** · 11-29-2009, 02:44 PM

Here's a couple pics of the balls. They should be brand new because the previous owner told me he never reinstalled the unit after putting in the refresh kit. Makes sense to me seeing how clean everything is.

I did not remove the ball races because I did not know how they come out, and I didn't want to wreck anything before finding out more. I notice there is just a gap between the upper and lower ball races. Is that how it's supposed to be? How are you supposed to get the races out? I definitely did not entertain the idea of prying up on them with a screwdriver. I don't want to wreck anything until I knew better.;)

Also, how tight are the bolts supposed to be? The bolts holding down the ball race retainer were just hand tight, as were the bolts that attach the front and rear case covers. Likely because the previous owner was under the impression that he required a shim kit. I understand shimming the impellor, but what about the races? Do the shims usually go in between the races? Or do they usually go under the race retainer to put more pressure on the balls? How does a guy tell if these are actually needed? Or was the previous owner just misinformed?

I don't have a meter type torq wrench at home, just an adjustable click type, so I'll have to borrow one to check the input shaft tension.

Thanks for the help so far guys and I hope you enjoy the pics. Please point out if you see anything in the pics that looks wrong!

**Michael** · 11-29-2009, 04:17 PM

Mmmmm... a veritable cornucopia of SN pics... nice.

I don't see anything "missing" with respect to the supercharger internals. Looks to me like it's all there.

As for the impeller, I believe that is the upgraded or HO unit (good for about 6 to 6.5psi); SN2000s came stock with the same impeller as every other SN supercharger, good for about 5psi of boost. If the previous owner replaced the stock impeller with this upgraded one, it would certainly explain why he paid as much as he did for the "rebuild" kit.

I should also mention, the probable reason why you didn't receive the 'stock' impeller from the previous owner is because (I believe) Paradise Wheels takes in stock impellers as partial trade-in towards the price of an upgraded impeller (I think the cost of the upgraded impeller is reduced by about $100 by taking advantage of this trade-in). The previous owner may have done this.

**JPJP** · 11-29-2009, 10:49 PM

The impeller in the pic is the HO impeller. Paradise Wheels sells the HO impeller for $150.

NOTE: Edited for false posting a few minutes ago.

**Michael** · 11-30-2009, 02:28 AM

For reference, here's a photo of the stock SN impeller. Notice the much more straight blades of the stock impeller versus the cupped blades of the HO impeller posted above:

**444** · 11-30-2009, 02:36 AM

Well that's good to hear someone else spent the money on the impellor upgrade. The seller never mentioned it.

I did a bit of searching and found some good info on the shims and how they affect clearances and tension on the ball drive, but I still have two main questions I didn't find answers to. First, what are bolts for the ball race retainer supposed to be torked to? And second, how do you safely remove the races? They seem to be in there pretty good, even with the retainer removed.

**Michael** · 11-30-2009, 02:39 AM

Originally Posted by JPJP

Paradise Wheels sells the HO impeller for $150.

Is that the price outright or with trade-in of a stock impeller? I can't seem to find the Paradise Wheels website so I can't verify this, but if memory serves me correctly, Paradise takes in good used stock impellers for a reduced price on the HO impeller. In contrast, CUNDN Racing doesn't do this, and only sells HO impellers outright.