Question(s) for those who've rebuilt their SN's...

[Michael]

hey, really likeing where this thread is goin, doin a great job with the pics and descriptions.

ill be watching for updates

ive had my 89 sitting on a shelf for close to 3 years now. started making a weird almost buzzing noise, tor it appart and found the impeller shaft had a small nick in it. everything else looked perfect.

figured on sending it out for a rebuild, but after reading through this thread i think i may try it myself


also the drive balls look un harmed, took the unit off immeditely after i heard any noise, anyone think it would be a bad idea just to replace the impeller shaft and save myself 300 bucks?

Welcome to SCH.

Replacing the worn impeller shaft yourself is certainly not a bad idea at all. I can't recall the price of the impeller shaft itself (I think it's about $100-$140, but don't quote me), but doing the job yourself is easy. There's plenty of reference material on the site here to sift through.

I would, however suggest that you also consider buying new drive balls and possibly new races as well. Even though you removed the blower once you started hearing a strange noise (very smart on your part, BTW) I would imagine the drive balls sustained some - although probably miniscule - damage, so it would be wise to change them. And for the cost, it's not worth the risk to continue to run the old balls.

I haven't updated this thread in a while, but I will very soon. I'm just about to finish polishing all the main blower parts; the oil case and main housing are polished to a mirror finish, but I'm still working on the scroll cover... it's intricate so it's taking a while. But I'll post photos of the polished bits soon.

Then, I'll post photos as I go through the reassembly process. Hopefully I'll have my SN89 reassembled within the next couple of weeks... if not sooner.

[Charged87GTA]

yea a quick search on ebay and the impeller shaft is 185, and a refresh kit is 150, but comes with the balls, front and rear seal, the two bearings and the o ring.

probably not a bad idea to spend the extra 150. just gotta be careful putting it back together so id dosent explode.

i think it may of been over spun to begin with, do you know the formula to measure the pullys and find out?

[Michael]

Call Paradise Wheels. Their prices for the impeller shaft will be lower than $185.

And while the refresh kit comes with new balls and seals, replacing the seals isn't easy. If all you need to do is replace the impeller shaft and the balls, it's a relatively quick job. Things start getting a bit more involved when you're talking about replacing seals, and in your case it's probably not needed.

There is an excel spreadsheet on the site here that allows you to calculate the pulley size(s) for a desired supercharger RPM. The internal step-up ratio of these blowers is 4.44:1 and they should be spun between 39,000 - 41,000 RPM max. Any higher and the wear becomes excessive; there's not much more boost to be had either.

Here's the link to the spreadsheet: http://www.superchargerhelp.com/showthread.php?t=4907

Hope that helps.

[Charged87GTA]

was actually just trying to find paradise wheels site for compairison with no luck. would you happen to have a link to the site or there number?

also ill pull it back appart today and see how everything looks on the inside of the blower

[Michael]

Unfortunately Paradise Wheels doesn't have a website. But here's their contact information:

Craig Conley
Paradise Wheels
1-760-740-0954
conleyr107@sbcglobal.net

They're in California, so be mindful of the time difference.

[pavement pounde]

When the impellershaft is worn then the balls are out of round to, it just is not visable by the eye.
Better replace the balls to when you do the impellershaft.
A little cheaper, the balls can be bought here to: http://cgi.ebay.com/ws/eBayISAPI.dll...=STRK:MEWAX:IT

It is the corect size and I used a lot of them

[Charged87GTA]

yea i had talked to them at paradise before, thanks for the info

and yea thats a lot cheaper for the balls. twice as many for less than half as much as they are from cundn.

no issues with them in your blowers?

[JPJP]

Craig at Paradise says the balls are supposed to be grade 5 or better. He sells grade 0. The balls are also supposed to be "sacrificial". Those on E-bay or McMaster are way too hard.

If anybody has had success using the grade 25 and harder balls like in the link mentioned above speak up because it contradicts Craig's advice.

[Joo]

I'm not familiar with the American standards. As I have read ( http://en.wikipedia.org/wiki/Ball_(bearing) ) grade numbers are related to the tolerances and surface and not to the hardness.

[JPJP]

OK I will slow down.

Grade 25 according to Craig is too loose a bearing tolerance. They must be grade 5 or better.

Also, the balls are supposed to be the sacrificial element. Having a Rockwell 'C' of 60+ is way too hard if they are supposed to be the wearing element. This is info. I am passing on from Craig at Paradise.

[Michael]

Joo is absolutely correct. The ball grading refers to tolerance, sphericity, and surface finish. The lower the number the more accurately produced and smoother the ball is. So a Grade 0 ball is more accurate to it's stated dimension, and has a smoother surface finish than a Grade 5 ball, which is more accurate and smoother than a Grade 25 ball, and so on.

The grade has nothing to do with hardness. That is a separate measure.

And Craig is correct: the balls are sacrificial. It may sound very contradictory to conventional ideals, but they are supposed to wear.

The best way to keep an SN running for a long time is to run an oil cooler and to change the fluid on a regular (and consistent) basis.

[JPJP]

Of course he is correct, I never said that grade 25 had ANYTHING to do with hardness. The balls listed on the E-bay link are also hardened in addition to being grade 25...........that is what I was talking about when referring to hardness. I am sorry if my wording confused anybody.

The E-bay balls are too loose a tolerance. The E-bay balls are also too hard.

[Michael]

Sorry JPJP, didn't mean to imply that you were wrong. Just merely trying to help Charged87GTA get a clearer understanding with respect to the drive balls' grading system vs. hardness. To be honest, I didn't even click the eBay link until now. And you're right - those eBay balls are both too low a grade and too hard.

I think it might also be important to mention, there's nothing that says harder balls can't be used... it just means they will wear the impeller shaft, ball carrier, and races quicker. And I doubt the lower price of those eBay balls will offset the cost of more frequent rebuilds.

[pavement pounde]

Mmmh, never thought of it that way.
Aldough I used them a lot and everytime I opened up the case I replace the balls.
I have not yet have to replace the impellershaft more often dough.

[JPJP]

Glad to hear of no problems with those balls pavement pounde and the impeller shaft holding up to them.

Thanks Mike, I was getting frustrated that I confused so many people.