SC12 service guide

 

This is a guide to help people through the process of servicing the SC12 supercharger.
 

This job should only be done by a qualified technician with the proper skills and tools.
 

We do not take any responsibility or liability for how this guide is used or the outcome from attempting to service a supercharger using any information contained within.

 

This guide is not meant to replace or superceed the factory service manual. It is intended to be used in conjunction with the manual. For this reason I do not include most specs like torque values or other important information because it is in the manual and should be the first reference for this information.
In servicing these superchargers.
I have learned a few tricks as well as some important things to look out for on these 25+ year old units that will be helpful to someone trying to attempt this for the first time.

 

One spec that I have changed is the supercharger oil volume. The book recommends 130 cc but I have found that does not reach the full mark on the dipstick.
I sell oil in 140ml units to make sure you have plenty available and I use 140 ml when I fill the case.

 

Gasket kits, bearings, oil and seals can be found here.

http://www.matrixgarage.com/?q=store/superchargers-parts-accessories-and-maintenence

 

We also have shims for adjusting the pulley gap but you will want to measure yours first and email us to let us know what you need.

 

Once you get the supercharger on the bench it's a good idea to first measure the clutch travel. This will give you an idea of how much you will need to change your shim thickness to get it into spec on reassembly. I don't say if because I have never encountered a clutch that was in spec.

You will need to anchor the supercharger to whatever surface you will be measuring off of. You can use clamps, a vice or any number of other things as long as it anchors it firmly to the surface you are measuring off of.

 

You will need a power source to engage the stator capable of delivering 12v at about 10 amps to ensure a complete engagement. A battery, battery charger, booster box or power supply are all good examples as long as they can provide enough amperage.

 

You will also need a way to feed the power to the stator. Small alligator clips that fit into the connetcor works very well.  Be very careful not to arc your leads against the supercharger or your work area.

 

Lastly you will need a dial indicator and a good mounting solution. A magnetic base works great. My vice is conveniently located next to my welding bench so I often use that.

Use the procedure in the FSM to inspect the clutch travel. Check in 4 different spots evenly located around the clutch and then average the numbers to find your average gap.

 

The first time you power the stator the clutch will pull in more. I like to do that once then take power off and let the rubber relax a bit. Once it mostly stops moving I will zero the dial indicator. Power it up and measure how much it changes. I like to do it a few times in a row to make sure I get consistent results.

Keep track of your numbers so you can use them to choose your shim size for reassembly.

 

This is a good time to test the resistance on the stator per the BGB. If it passes it should be good to reuse. If it fails it likely needs to be rewound. We can provide this service if it's needed.

 

Now it's time to start taking it apart

 

A 3/8 impact works very well for breaking the drive plate nut loose. If not you will need to devise a way to hold it. A strap wrench or large channel locks would likely work. I cut my own spanner out of a 2x4 piece of wood so that I wouldn't mar the drive plate when putting everything back together after paint or ceramic coating.

I recommend devising a way to hold it because you will want to torque the nut on reassembly.

 

Pull the drive plate off and remove the shim sitting right under it.

 

Next step is to remove the pulley. This requires a SST. I made my own by welding a socket to a washer and then welding 4 woodroof keys to the washer.

The first unit I took apart I used a punch to loosen it but I consider this to be a very important component to torque properly so I do not recommend any method that won't allow you to properly torque it on assembly.

 

If you are interested in purchasing a SST feel free to contact me.

 

Remove the pulley nut and then the pulley should slide right off.

 

You will need a set of large snap ring pliers to remove the snap ring holding the stator on.

Now the stator should slide off. If it resists try tapping it with a rubber mallet.

The area between the stator plate and snout flange is one of the worst rust spots on the supercharger.

Next remove the 5 bolts holding the pulley snout on.

The snout can be a little stubborn to get off. You can use a 3 jaw puller or you can use a chisel to tap under the ears on the flange. Be very careful and only do a little on each ear at a time or else you can break the cast snout.

Use a wire brush or wire wheel to clean up the area under the snout and the rest of the suptercharger housing on that side. Make sure to get all the rust, oxidation and grime off especially where the snout sits.

 

Remove the vacuum port bracket held on by the nut on the bearing cover.

Remove the bearing cover.

Wipe out all grease and clean it up as well as possible. Make sure not to get any foreign debris in there.

 

 

Now you will want to clean up all the steel components.

Grit blasting is the best option but what ever method you use make sure to remove all rust.

Inspect the back of the stator plate and make sure the rust isn't too severe. This is a very common rust point and can lead to weakening the plate enough the stator will suck it's self into the pulley. This becomes a very expensive repair.

Make sure the stator plate is flat on the back.

On the left is a stator that rusted out and sucked into the pulley. On the right is a healthy stator plate.

If the stator plate is damaged beyond use you can send it in to us for repair.

 

I highly recommend coating all these parts in the most rust resistant coating possible.

The tolerances are very tight in many areas of this assembly. Do not use thick coatings.

I use http://www.cerakotehightemp.com/ ceramic coatings as the go on very thin, are incredibly hard and bond very well to a properly prepped surface.

 

You can send these components into us to be ceramic coated if you want a thin very hard surface that will hold up for the life of the supercharger.

 

It is best to replace the pulley bearing before coating it since this process can damage a fresh coating.

 

This is not a complex procedure but it can be quite easy to damage the pulley if you apply any force in the wrong area.

The first step is to remove the flare holding the bearing in place. I prefer to use a flat or slighlty rounded puch to tap them back out so you don't have to remove any material.

 

Once it looks like the bearings path is pretty clear you are ready to press it out.

Whatever you do only apply pressure to the bearing and the cylinder surrounding it. If you apply any pressure to the face or outer edge of the pulley you can bend it and it will be useless.

Use a sleeve on the back side of the pulley with an ID just bigger than the bearing.

 

On the front side use a rod or tube that fits tightly in the bore of the pulley and contacts as much of the bearing as possible.

 

I found that iron plumbing pipe is sized well for both sides of the pulley. I forget which size I use but the front side is one size smaller than the back side.

You can use a shop press or a large vice. I use my shop vice so I don't apply too much pressure.

Once the pulley is set up in the vice I hit the steel surrounding the bearing with a propane torch just enough to get it warm. You don't want to get it too hot but a little heat helps. Then I start pressing the bearing out. It will take a bit of pressure to get it to unseat and then it will get easier as it comes out.

Make sure the front and rear shaft stay square to the pulley and make sure the bearing is pressing straight out.


Once the bearing is out clean up the bore with a scotchbrite and then wipe it out with a rag and cleaner like isopropyl alcohol.

Take loctite red and smear a little around the top of the pulley bore and the outer race of the bearing.

 

Now you will need to put the larger sleeve on the front of the pulley. You have to make sure it sits concentric and square to the pulley and resting only on the supported area around the bearing.

If you do not do this and apply force to the outside of the pulley you will destroy it.

Use a large flat plate on the bearing side to start it. This will help insure the bearing starts square to the bore and aligns properly.

Press the bearing in until the plate gets close to the back side of the pulley.


From here I use the old bearing to press the new one in. Whatever sleeve or rod you use must focus the force on the outer race, apply pressure evenly and not apply any significant force on the seal or inner race.

Once everything is lined back up press the bearing the rest of the way in until you feel it bottom out.

 

After you pull the pulley out of the vice or press use a .002” or .05mm feeler gauge and try to slide it between the bearing and the pulley. If the feeler gauge slides in the bearing is not seated fully and you must press it more.

Once the bearing is fully seated use a center punch next to the factory punch marks to flare the lip out to further secure the bearing.

 

 

Now you can prep for your coating.

 

Mask off the bearing making sure no abrasives will get into the seal or inner journal. This is especially important if you are bead blasting.

 

I do grit blast the friction surfaces of the pulley to give them a roughed up texture to grab when engaged.

After blasting I mask off the friction surfaces because you don't want them coated.

Next is coating.

 

 

Once the coating is cured  it's time to reassemble the pulley side of the supercharger.

 

Pack white lithium bearing grease around the bearing and in the cap. I prefer to over fill it so a little will squeeze out as I tighten the cover down. Doesn't have to be a lot though.

If you have a new gasket you shouldn't need any sealant. If you are reusing your gasket then apply some FIPG or similar to both sides before setting it in place. Put the cover on and torque the two bolts and stud.
Put the vaccum manifold back on.

Next prep the snout for assembly.
I like to coat the entire area the snout rests on with antiseize. This should help prevent the SC housing from further oxidizing. If you have coated the SC housing and snout it isn't necessary to coat the flange area but still a good idea to coat the shaft and splines.

Bolt the snout back on.
If it resists use the bolts to take it in little bit by little bit using a star torquing pattern.

Torque the snout bolts per the BGB.

 

Make sure the weep hole in the snout flange is unobstructed so water can drain out. I like to use an air blower to blow it out and make sure it's clear.

 

Put antiseize on the snout. Try not to get any on the threads but coat the rest all the way down to the base.

Put the stator on making sure you align the pin on the stator with the locating bore on the snout flange.

Once it is bottomed out put the snap ring on.

Take a punch and tap the snap ring down and towards the center. Do this in a pattern around the snap ring a couple times around.

 

 

Next install the pulley

Apply a drop of loctite red to the threads of the pulley nut and torque it to the BGB spec.

Next step will be shimming the drive plate

 

I like to shim the pulley on the tight side of spec because of that additional flex on the pulley and because it will wear over time.

Take the average of the gap you measured when you tested it earlier and then subtract the minimal gap listed in the book. We will call this value x. This tells you how much thinner your shim needs to be.

Use a micrometer to measure the drive plate shim.

Now take the thickness of the drive plate shim and subtract x from the thickness of the shim. This tells you how thick your shim needs to be.

Since we used the minimal tolerance you will want to use the next thicker shim that you can find. This should get you as close as possible to the low end of the spec while still being in spec.

 

If you need shims contact us with the thickness required.

 

Put the shim on the drive plate shaft and then put the drive plate on and torque the drive plate nut.

 

Check the pulley gap again. If it's in spec then you are good to go. If it's out of spec add a thicker or thinner shim until it's in spec.

 

Now that the drive side is complete first drain the gearbox oil and then pull the gearbox cover off. Do not remove the last two bolts holding the rotor cover to the SC housing. I do not recommend taking this apart. You risk damaging seals and bearings that cannot be replaced.

Clean out the gear box keeping an eye out for metal filings or unusual debris.

Inspect the gears for unusual wear or damage.

Spin the drive plate and make sure it spins smooth and free.

 

Clean up the gearbox cover and wipe down the sealing flanges.

Even when using a new o-ring I like to use a little sealant. I use the thinnest possible coating I can get spread evenly on the flange and in the cover groove. It shouldn't be needed but is a little extra insurance.

 

Install the o-ring in the cover groove.

If using an old o-ring it may be best to use a little more sealant to make sure it seals.

 

Mount the cover back on to the supercharger.

 

Put a new copper washer on the drain plug and torque it back down.

If you removed the dipstick extension put a new copper washer on that and torque it back down.

 

Fill the supercharger back up with oil.

 

If you have a MG service kit you will also have a new dipstick sealing washer.

 

Now your supercharger service should be complete.

 

courtesy of webmatter.de