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

**Michael** · 05-27-2011, 05:36 PM

Thought I'd try and bring this discussion back on track by posting a few photos of my SN89 rebuild progress.

The last while I've been trying to polish the major components back to their original mirror-like finish. A friend of mine has a full-sized buffer at his shop and he's gracious let me use it when he doesn't need it (which, luckily, is often).

Below are some photos of the front oil case and main scroll housing. I'm still working on the rear scroll cover. Because of it's intricate design, it's taking a little longer than I thought... but I'll get it close to looking like these.

Once the rear scroll cover is polished up (along with the discharge tubing), I am going to begin the reassembly process. Stay tuned.

**winfred** · 05-27-2011, 08:23 PM

I am running 2 lube coolers in series as I don't have the room for one big one. Never ran it without the cooler in place, just without water in it, best example I have of how well it works is I did a run from 55-145mph and intake temps only came up 22 degrees. Air to water units are generally super low restriction, usually something like .05# loss at 15-20# compared to .5# for a air to air, I am not running enough through it to really expect much loss, 8-8.5# boost with upgraded impeller on sn92 spinning around 41k (can't remember exactly as it's been a while 5.5 crank 3.5 blower 6500 redline) with very little dust on the housing so my belt routing design mush be working

Originally Posted by Michael

Only 6-10deg over ambient is impressive. If it's working for you, then by all means don't change a thing. My suggestion to use a water/meth system was merely mirroring what I've read on this (and other) forums.

Are you running an oil cooler as well? Did you see more boost before you had the intercooler installed?

**Charged87GTA** · 05-28-2011, 11:32 AM

thing looks great polished up

went over mine with a wire wheel, thats all im doin cuz everything else under the hood is mostly bare alum

**Charged87GTA** · 06-02-2011, 08:12 AM

well got everything back together yeasterday and the blower sounds pretty good, keeps blowing the pipes/hoses after the blower off lol. sounds like an airplane when its not hooked up to the motor

time to invest in some heavy duty hose clamps

the car was hard to keep in a straight line before, gonna be real tough now as long as i can keep it in boost

**Charged87GTA** · 06-02-2011, 08:14 AM

also if anyone knows the formula to see if your overspinning the blower i would apprecieate it if you could share it, been searching for it and cant seem to find it.

my sbc revs pretty high, i have a 7000 rpm chip in it and it gets there real quick with the blower on. just trying to make sure its safe, thanks

**Michael** · 06-02-2011, 08:22 AM

Originally Posted by Charged87GTA

well got everything back together yeasterday and the blower sounds pretty good, keeps blowing the pipes/hoses after the blower off lol. sounds like an airplane when its not hooked up to the motor

time to invest in some heavy duty hose clamps

the car was hard to keep in a straight line before, gonna be real tough now as long as i can keep it in boost

Congratulations on getting the blower back together and on the car. See? These old Paxton's aren't so hard to work on, are they?

Originally Posted by Charged87GTA

also if anyone knows the formula to see if your overspinning the blower i would apprecieate it if you could share it, been searching for it and cant seem to find it.

my sbc revs pretty high, i have a 7000 rpm chip in it and it gets there real quick with the blower on. just trying to make sure its safe, thanks

Did the excel spreadsheet not work for you? I posted the link to it back in post #48 of this thread. All you have to do is enter the pulley sizes you're using and it will tell you how fast the blower is spinning @ the maximum engine RPM. If it's too fast, then look for a larger blower pulley that will spin it slower; input the pulley diameter into the spreadsheet to see what RPM it will result in.

If you're spinning the engine to 7000rpm, then it might be a bit high. Most of the GM V8s from the era of your GTA only spun to about 5500rpm, and the Paxton kits were pullied appropriately. Since you're spinning the engine 1500rpm higher, then you might want to consider changing the blower pulley.

**whodwho** · 06-02-2011, 08:23 AM

Crank pulley \ SC pulley X 4.4 X Engine rpm = SC RPM

**Charged87GTA** · 06-02-2011, 09:23 AM

yea they dont seem that bad now, i mean the car is built to handel the rpms, not sure on the blower, bought the car the way it was and didnt get a whole lot of info on it, i do know he ran the blower alot and that that the car ran high rpms, so maybe the pullys are meant for the car, they are the triple belt type.

hopefully it all holds together when i get the piping all sorted out.

hows your 89 coming?

**Michael** · 06-02-2011, 11:09 AM

Originally Posted by Charged87GTA

yea they dont seem that bad now, i mean the car is built to handel the rpms, not sure on the blower, bought the car the way it was and didnt get a whole lot of info on it, i do know he ran the blower alot and that that the car ran high rpms, so maybe the pullys are meant for the car, they are the triple belt type.

hopefully it all holds together when i get the piping all sorted out.

hows your 89 coming?

The rebuild is not moving as quickly as I would like, but it's coming along. I've taken the H.O. impeller and ball carrier to a local shop that specializes in high-performance coatings. I'm getting the impeller ceramic coated and the ball carrier dry film coated. I'm hoping the ceramic coating on the impeller will help drop the inlet air temperature a bit, while smoothing out the incoming air flow and giving a bit more CFM and/or boost. I'm hoping the dry film coating on the ball carrier will provide some wear resistance over the long run. I've never seen or heard of anyone ceramic coating an impeller or applying dry film lubricant to a ball carrier before so this is going to be a bit of an experiment. Can't do any harm... I hope.

But once those parts come back (hopefully tomorrow, if not Monday), I'll be able to start the reassembly process. I'll post pics of the coated impeller and ball carrier when I get them.

I should also mention, I am working on having this shop become a forum supporter. I am working on a deal to give forum members here who want to ceramic coat their impellers a package deal. The price would include shipping to and from the shop anywhere in Canada and the U.S. We haven't talked about international customers yet.

The only unfortunate thing about this is I don't have any "pre coatings" data to prove whether they will make a difference. And since my blower is still a ways from being bolted up to my car, I can't say with any certainty when I'll be able to report anything. But if anyone here wants to try this experiment to see if a ceramic coated impeller will result in a drop in inlet temperatures and/or boost, feel free to send me your impeller and I'll have this shop ceramic coat it for you and send it back. Shouldn't take more than 7-10 business days.

**whodwho** · 06-02-2011, 11:59 AM

Interesting idea playing with the ceramic coatings, with the surface area and mass of the housings I would think they would be a bigger source of heat and might help from heat soaking if coated as well? I guess it comes down to what is most of the heat source, the ball drive or compressing the air??

Have you hit them up if it is possible to coat the inner airways of the housings?

**Michael** · 06-02-2011, 12:20 PM

I thought about ceramic coating the scroll cover too. You're right - it is a much larger piece, and would probably prove to be a larger heat sink than the impeller. However, my fear is that ceramic coating it would promote heat retention within the blower itself (much like it does on an exhaust system); my thinking is that ceramic coating the impeller will help to deflect some of the heat created by compressing the air which occurs between the impeller and housing/scroll cover. Will it work? No idea, but it's worth a shot.

I should mention, this shop does have a heat expulsion coating too, which helps to radiate heat away from the part itself. The owner of the shop said that he's applied the coating to a number of race car parts; the appearance of this coating isn't "pretty", so he's only used it when appearance/aesthetics weren't important. I would have had this coating applied to my entire supercharger, but frankly I like the mirror-finish look... LOL!!!

I think both the process of compressing the air, and the ball-drive produce substantial amounts of heat. The ball drive's heat can be kept in check by the use of an external cooler; the compression process will be more difficult to control.

I didn't ask about coating the inside of the housings, but I can do that next time I'm there. I'm sure they will be more than happy to do it... I'm just not sure if it will result in lowering the blower's temperature or keeping the heat inside.

**Buck-Strickland** · 06-03-2011, 11:52 AM

Hi Michael,
I’m curious about the “dry film”. Could you expand on your idea of the benefit there?

**Michael** · 06-03-2011, 12:07 PM

Funny you should bring that up... I just got off the phone with the coating shop. Turns out the parts won't be ready until Tuesday for me to pick up.

My thoughts behind the dry film was that since the ball carrier itself doesn't actually place any pressure on the balls (that's done by the two bearing races), that by applying dry film lubricant it'll minimize the wear on the carrier itself.

Obviously, friction has to exist between the balls, the bearing races, and the impeller shaft, otherwise the ball-drive itself wouldn't work. Which is why I didn't have the impeller shaft and races coated. But the ball carrier just transfers (for lack of a better word) rotational (or sideways movement depending on how you look at it) to the balls and holds them in place as they spin.

I doubt there will be any performance benefit to this other than MAYBE reducing oil temps a tiny amount. All I was really looking to do was to give the ball carrier a longer service life by reducing wear; I doubt it will have any impact on the balls, races, and impeller shaft.

Now that I think about it, I hope I haven't screwed myself... if this coating DOES reduce friction with respect to the ball drive system, does that mean I'll see a different turning torque value when everything is back together? Oh oh...

Me and my bright ideas.

**Buck-Strickland** · 06-03-2011, 12:51 PM

It will be okay. The resistance is all in the compression of the balls by the races. Otherwise the seals and misc. contribute a minor percentage to the rotational torque reading. I can’t see any reason dry filming only the carrier would impact your readings. It is a relatively soft metal, mines brass, and I do see wear. It would be interesting to see your coated carrier after some hard use.

**whodwho** · 06-03-2011, 12:59 PM

Originally Posted by Michael

...since the ball carrier itself doesn't actually place any pressure on the balls (that's done by the two bearing races), that by applying dry film lubricant it'll minimize the wear on the carrier itself...

I'm confused on your statement, the ball carrier drives the balls from the input shaft so there is high pressure between the carrier and balls??