I know this topic has been thrashed, but I am going to join in with my 2c worth.
 
I am returning my AW11 SC to factory spec, and the SC12 is a problem - lets face it, who's isn't .. The SC12 is a very basic design, it's only moving parts are the lobes, they are connected by a couple of 1:1 gear set but basically it's driven at a ratio of the harmonic balancer and the pulley. The lobes are Teflon coated to about .3 - .5 mm (this is really thick).. There are 4 bearings and these are the problem. There are 3 different sizes, 17x46x21 in the gear end, and 17x15x 14 & 18 in the pulley end. There are a couple of odd design decisions made by Toyota - the smallest bearing also has the highest lateral pressure as it has the pulley tension on it. All bearings are held in place by a groove in the bearing outer and case which is injected with epoxy. This is more than likely used to stop the aluminium case expanding and releasing the bearing when hot. It took me near 12 ton to break the epoxy and release the bearings, and I think I may have popped out a poo when I was nearing the 12t mark waiting for the massive bang....
 
Anyway, most of you would already know all this - and you would also know that the bearings are very unique and even though I have Koyo, SKF, and a couple of other part numbers, are unobtainable. However - my plan is this - I have located very high precision bearings with massive specs that are available with the 17mm shaft size, they are larger in diameter. I will be machining the casing to fit these and as they are slightly narrower than oem it allows for a rebate in which I will put a retaining clip.
 
The lobes tolerance is important as they must be a beez dick from each other and the case - over time with dust, vibration, swelling etc they wear - but only on the outer edge and by no more than about .1 mm. Leaving this would not result in a massive boost drop, maybe a psi or so. I intend to re-Teflon the outer edge as a 'topup'. The main thing is balancing, I want to balance the lobes laterally to increase the precision, and mainly to reduce any vibration.
 
With the new bearings and their high spec (good for 50K RPM continuous), and with the balanced lobes. I see no reason why the SC12 cannot hit 20K RPM reliably. It will depend on the amount of heat generated, but this is should be lower with good internals.
 
That's my plan - I will keep this thread going with updates - then if it's all successful, I may be able to offer a rebuild service, or at least all the info to DIY...
 
Specs:
 
SC12 produces 1.2L of air per revolution
1:1 @ 7000 engine RPM = 8.4L/Min = approx. 8 PSI (AGZE Config)  (SC12 RPM = 7000)
1:1.3 (avg pulley upgrade) @ 7000 engine RPM = 11L/Min = approx. 10 PSI (SC12 RPM = 9100)
1:2 (potential) @ 7000 engine RPM = 16.8L/Min = approx. 16 PSI (SC12 RPM = 14000)
 
The std computer would not handle this boost - the motor would run lean..
 
 
 
 
 
 
 

Interesting proposal, Keith.  I'll keep eye's and ear's on this, see how you go. 

I will be watching with interest too as I have a couple of SC12's stashed away which I would like to rebuild as spares. Have you already found someone who is able to recoat the lobes?

A quick thought off the top of my head . . . is it going to work out cheaper per unit to do a run of lobe re-coating? There may be a few more SC owners out there who could be in for a group effort on this project.

If that should happen to be the case, put me down for 2 SC's straight away.

Hoping to contribute a bit of food for thought via a bit of thread derailment... If your just wanting to rebuild the SC12 to keep the car period correct and not chasing more performance, you can probably ignore the rest of this post :D
 
I looked at similar ideas of fixing up the SC14 superchargers (like how hard is it to get some bearings to fit and do a little machine work???), but decided to go with a better super charger since spinning the SC12/SC14 any faster brings diminished returns as it just converts crank HP into fire (I believe the rotors expand under extra the heat and this leads to the teflon chewing itself off against the casing). I ended up deciding on the Eaton M62 supercharger, which can be had for a couple of hundred on ebay. The M62 is a 1L/Rev, has a recommended max rpm of 14000rpm and has been proven to run on a large amount of motors from 1.6L to 4L with varing boost pressures.
 
The reasons I like the Eaton besides them being cheap, is the fact they are completely rebuild-able, they have many configurations (used on many factory cars), it has a factory by-pass valve, and you can still buy parts brand new for them. All the bearings, rotors, snouts, couplers, pullies, all serviceable! Check out the range of parts available from Jon Bond Performance (JBP) - https://jonbondperformance.com/
 
For the eventual restoration of my SC AW11, I bought an M62 from a Buick for $300.

 
In comparison to my SC14


 
Now, as you see, it is too long to fit where the stock SC12 goes, however JBP have a 2.5" long snout drive that will fit the M62.

 
I can either cut down the rear inlet of the Buick M63 housing or swap over to a Nissan X-Terra/Frontier M62 case.

 
Alternatively, you could fork out the cash for Mercedes M62 which is a more compact unit and has an electric clutch on it. However these go between $800 - $1600 on ebay.

 
With either shortened down M62, it should fit quite happily along the side of the 4A block

 
 

spike10000
I will be watching with interest too as I have a couple of SC12's stashed away which I would like to rebuild as spares. Have you already found someone who is able to recoat the lobes?

dennis the menace
A quick thought off the top of my head . . . is it going to work out cheaper per unit to do a run of lobe re-coating? There may be a few more SC owners out there who could be in for a group effort on this project.

Jon Bond Performance does re-coatings for the Eaton range of superchargers, might be worth contacting them to see if they could also do the SC1x's
 

Good post - Having gone the rotrex route and seen boost in the vicinity of 26PSI, I've decided to go back to period specific for the car. Shannons insurance de-valued the car and after a lengthy chat with them they agreed that I could re-value if the car was totally stock and 100% perfect. That's my challenge now, hence the rebuild of the SC12.
 
 

Anyone willing to part with an SC12 ? - I need another for parts ?

I've an SC12 in pieces, not sure how good they are, but they came with the SC14 I bought. PM if your interested :)