I’ve been in two minds as to whether I should include this section or not, due to some of the re-builders listed in the Vendors section of the site advising me that a rebuild was best left to a qualified person. Given the fact that service parts are difficult to come by, and as a rule tend to be expensive (HOW MUCH! – for a few bits of rubber and a couple of steel balls!), for what they are, and if sufficient care is not taken during a rebuild the supercharger will fail within a few thousand miles.
However, due to the fact that rebuild information is generally available, in the guise of the McCulloch, Studebaker and Kaiser shop manuals, as well as various magazine articles (listed in the recommended literature section), and the fact that knowledge of the rebuild process can lead to a greater understanding of the mechanics of the supercharger, I decided that I would include rebuild information. Please understand though that if you decide to rebuild yourself, then I will not be liable for any damage to the supercharger, your car’s engine, and the expense should the supercharger require another rebuild. I personally recommend that you send the supercharger to an experienced re-builder.
If you do re-build yourself, the following precautionary methods should be observed during the rebuild operation. Failure to follow these will practically guarantee supercharger failure after the rebuild:-
CLEANLINESS – Work only upon a clean, hard surfaced bench. All tools and wiping rags should be free of dirt and deposits of oily grit. Also, all containers should be clean and only fresh, clean solvents and oils should be used during the rebuild.
PROPER TOOLS – The use of proper tools will reduce the possibility of damage occurring during disassembly and assembly procedures. The supercharger is a precision built engine accessory and “brute force” is not required for maintenance and repair work. At the end of this page I’ve listed details of the special tools required to enable the disassembly and assembly to be conducted correctly.
RUST AND OXIDATION – The working surfaces of the drive assemblies are micro-finished and the presence of either rust or oxidation will seriously damage the parts. For this reason, NEVER handle the output shaft, drive balls, or ball races barehanded. Instead, wear clean, dry cloth gloves or use well oiled patches of clean cloth to handle the parts. Provided they are available, lint-free paper wiping towels can be used for this purpose.
STEEL WOOL AND ABRASIVES – NEVER use steel wool, or any form of abrasive material, to clean the input and output shafts, drive balls or ball races, as such practice will destroy the micro-finish. Surface aberrations or pits, regardless of size, will result in noisy and rough operation and cause ultimate failure of the supercharger.
SHORT CUTS – There are no short cuts when you are working on precision equipment. Therefore, carefully follow all phases of the instruction information and you will avoid trouble.
All supercharger repair work must be performed with the supercharger removed from the automobile engine, or other mounting location. Any accumulation of oil, dirt, or grime should be removed from exterior surfaces by application of cleaning solvent and wiping with rags or industrial wipers. DO NOT immerse the supercharger in the solvent as damage to the solenoid regulator will result. Also, avoid the use of compressed air during this cleaning operation.
Also note that across the years the VS57 superchargers were produced the different variants sometimes had differences in the internal components. This rebuild guide is currently VS57S type specific and will be modified to allow for the differences when I’ve finally identified them.
Remove the oil dipstick, empty the lubricant from the oil sump, and then mount the supercharger to the supercharger holding fixture ST-107 (or equivalent). Use an old fan belt to hold the pulley taut (alternatively use special tool ST-103) and remove the cap screw, lockwasher and retainer from the variable ratio pulley.
Pull the fixed flange of the pulley along with the splined hub from the supercharger. It is possible that the flange will pull off the splined hub, or the flange/hub assembly is too frozen to be pulled by hand, in which case the stubborn parts can be removed at a later stage, by pressing the hub out of the pulley after the bearing housing has been separated from the scroll housing.
Remove the sliding flange by pulling it from the supercharger. Some resistance will be encountered due to the fit of the thrust bearing on the air piston, and pulling firmly on the flange should free the bearing from the air piston.
Push in on the hub of the air piston to compress the piston spring and remove pressure from the air piston cover. Insert a screwdriver in the notch at the bottom of the bearing housing and snap out the outer retaining ring. Remove the air piston cover and then snap out the inner retaining ring.
CAUTION: During removal of the retaining rings and air piston cover, the air piston must be held down constantly. After the inner retaining ring is removed, let the air piston come up slowly until the piston spring is full extended. This will prevent the possibility of personal injury resulting from the coiled piston spring forcibly ejecting the air piston from the air chamber.
The air piston and the piston spring can now be lifted from the air chamber of the bearing housing.
Remove the medallion and the solenoid regulator retaining spring. Remove the solenoid regulator from the bearing housing by grasping the top shoulder of the regulator with vise-grip pliers and then pulling it straight out. Remove the two sealing “O” rings from the solenoid regulator well.
Invert the supercharger and remove the scroll cover by first removing the retaining screws, and then lifting, not twisting, the cover from the housing. It may be advisable to scribe the scroll cover and housing prior to removal to aid alignment on reassembly.
Hold the impellor wheel firmly using special tool ST-103, or by using a triangular clamp bolted to the housing (see picture), and remove the hex head retaining screw. Insert the impellor wheel puller (special tool ST-104) into the impellor and turn it clockwise until the impellor wheel is lifted clear of the output shaft boss. Remove the impellor wheel shim, or shims.
CAUTION: The impellor wheel is precision machined and balanced to permit turning safely at speeds in excess of 25,000 rpm. Any chipping, deep surface scratches or gouging will destroy the balance and can result in serious damage when the supercharger is reassembled and operated. Therefore, do not use pliers to hold the impellor wheel while removing the retaining screw. Also, do not use a screwdriver or other tool, to pry the impellor wheel off the output shaft.
Should the impellor wheel be chipped, or badly gouged, do not attempt to dress out or repair the damage but, instead, replace the part. This is the ONLY safe practice under such conditions.
Replace the scroll cover on the housing and secure it with four of the retaining screws, lockwasher and flat washers placed equally around the rim.
NOTE: The flat washers must be placed between the lock washers and the surface of the scroll cover to prevent hogging or gouging of the cover.
Scribe the bearing housing and scroll housing, to aid alignment on reassembly and then remove the hexhead screws, lockwashers and flat washers which retain the bearing housing to the scroll housing. Remove the bearing housing by twisting it free of the scroll housing. After the housings are separated, remove the two sealing “O” rings from the bearing housing.
CAUTION: Do not use a screwdriver or other tool to pry the housings apart. To do so will result in either breaking out a section of the side wall of the scroll housing, or gouging of the mating surfaces of the housings. The latter, while not appearing serious, can cause loss of concentricity when the housings are reassembled, and result in damage to the drive system. Also, never rock the bearing housing back and forth to loosen or remove it. If the housing is rocked during the removal procedure, it may result in bending or damaging the input and output shafts and bearings.
CAUTION: The following must be observed:
1) Handle the internal moving parts carefully. Do not “throw” the drive balls, ball races, or other parts into containers. Pits, scratches, or surface aberrations will result in noisy operation and ultimate failure of the supercharger.
2) Do not handle the steel parts with bare hands. This can result in rusting and oxidation which will necessitate the installation of new parts.
3) To prevent rusting, keep the internal steel parts submerged in a bath of clean oil following removal. This is very important if the existing oil film is removed by washing with gasoline or commercial cleaning solvent.
4) Do not use steel wool or other abrasive material to clean or polish the contact surfaces of the planetary system. Once rust or oxidation has attacked the metal the parts must be replaced, not just cleaned and polished.
Remove the input shaft and oil pump assembly. If the shaft and pump assembly remained in the bearing housing when it was lifted free of the scroll housing, tap the pulley end of the input shaft with a rubber mallet to drive the assembly out of the housing.
Remove the race load assembly from it’s position in the scroll housing.
CAUTION: Do not attempt to disassemble the race load assembly without the use of an arbor press. The internal springs are exerting sufficient force to cause personal injury or damage to the assembly if released suddenly.
Remove the drive balls of the planetary system by lifting the output shaft until the balls are free of the rear ball race. The output shaft can then be removed by pulling it free of the scroll housing.
The ball races can be removed by lifting them from their respective seats in the race load assembly and the scroll housing. Use special tool ST-105 by placing it in the center of the race and using it as a leverage point for prying out the race with two screwdrivers.
Remove the hub key and the shaft-seal spacer from the input shaft and pull the bearing from the shaft. McCulloch recommended using special tool ST-106 and an arbor press to remove the bearing, a modern alternative would be to use a bearing puller. Spring the screen retainer off the lower end of the oil pump and then remove the screen.
Screw out the slotted-head plunger spring retainer and shake the coil spring out of the pump body. Provided that the pump plunger, or piston, failed to shake out, hold the pump body steady and rotate the input shaft until the plunger is at the high point of the cam. The pump body will now be free to slide off the input shaft.
CAUTION: Do not try to force the pump body off the shaft. Any binding will be caused by the pump plunger hanging in the camway of the input shaft, and several revolutions of the shaft will serve to free it.
Remove the bushing from the body by pushing it out in the direction of the staking tang. The small ball at the foot of the pump is staked in place and serves only to seal the drill passageway.
The last ball bearing on the input shaft may now be removed, using an arbor press and special tool ST-106, or a bearing puller. The ball driver can be removed by backing out the five retaining screws.
The solenoid regulator should not be disassembled. In the event of failure, the unit must be replaced.
Before starting assembly work, the work area should be well cleaned and all dirty rags or towels removed. The internal and external components of the supercharger should be cleaned and free of dirt and deposits of oily grit. When assembling the internal drive parts, particularly the planetary system, even lint and dust should be held to an absolute minimum. Also, all moving parts should be oiled as they are assembled using type “A” automatic transmission fluid.
NOTE: If the following instructions are followed step by step (even though some steps seem out of order), the assembly of the supercharger will be more easily accomplished.
1) Install the scroll cover on the scroll housing, retaining it with four screws, fit the housing into the assembly fixture, special tool ST-103.
2) Place a race pin in the recess in the side of the ball race housing.
3) Place a clutch disc in the seat of the scroll housing (it will be necessary to notch the clutch disc slightly to clear the race pin), and press a ball race into position over the clutch disc. The ball race should be a light tap fit with a plastic, or rawhide hammer. Be sure the race is bottomed against the clutch disc. In some later superchargers shims were also used with the ball races, and if your ball race has shims these should also be installed.
4) Turn the labyrinth rings on the output shaft assembly so that the gaps are 180 degrees apart, and insert the shaft (dowel pins down) into the center opening of the scroll housing. Angle the shaft slightly away from the gap in each ring as the shaft moves down, and straighten it to vertical as the top ring slides into place inside the bore. NOTE: A slight taper in the face of the opening helps to compress the rings as the output shaft seats. Also before installing the output shaft, check to see that the rings are in the first and third grooves of the shaft, and that the chamfer on the top ring is toward the impellor end of the shaft.
5) Place the five drive balls around the output shaft, then push down gently on one at a time to seat each in its proper place on the ball race. NOTE: These balls are furnished in matched sets of five. Never install less than a complete matched set. To do so can cause severe internal damage to the supercharger.
6) Place another race pin in the recess in the side of the race load assembly, notch another clutch disc to clear the pin, and place the clutch disc and the race in position in the race load assembly.
7) Place the race load assembly into position, ball race down, over the drive balls.
1) Install the ball retainer, or driver, on the end of the input shaft and tighten the retaining screws to a minimum of 30 inch/pounds.
2) Press the large ball bearing onto the input shaft until it is seated against the shoulder (the lettering on the bearing should be face down). Use an arbor press and special tools numbers ST-100 and ST-101.
3) Slide the oil pump body, with bushing insert, onto the shaft. CAUTION: When installing the pump body, make sure the pump is not upside down before installing the outer ball bearing. That is, when correctly installed, the bore in the pump body will align with the camway ground into the input shaft. Failure to so install will result in a complete lack of lubrication.
4) Press the small ball bearing into place on the shaft with the letters up. Use an arbor press and special tools no ST-100 and ST-102.
5) Install the oil pump plunger, plunger spring, and the oil pump lug in the oil pump body, and secure the screen to the end of the pump body with the screen retainer.
6) Install the inner air piston ring on the boss of the bearing housing, and lock the ends of the ring together.
7) Press the input shaft seal into position inside the bearing housing with the lips of the seal facing inward. Use special tool ST-101.
8) Install the sealing “O” rings (two required) in the inside and outside groves of the housing shoulder. NOTE: Do not install the ring or rings in the center grove. This grove is a part of the air passageway system and, if it is blocked, the control system will malfunction.
9) Place the oil level sleeve on the oil level gauge (dipstick!) and gently tap into position in the side of the bearing housing.
10) Lightly oil the two small “O” rings and install them in the channels within the regulator well. Oil the sides of the solenoid regulator and push it down past the two “O” rings until it is firmly seated.
11) Place the retaining spring on top of the solenoid regulator, and then install the supercharger medallion. NOTE: The retaining spring must always be in place as it also serves to ground the solenoid case to the supercharger.
12) Install the outer air piston ring in the groove of the air piston. (Location of the gap is not important).
13) Place the air piston spring in the nose section of the bearing housing and then slide the air piston into place. Oil liberally. Push in on the piston, depressing the spring, and install the rear retaining ring on the inside of the air chamber.
14) Install the dust shield, and secure in place with the outer retaining ring.
15) Use an oil can containing Type “A” transmission fluid, fill the bore of the oil pump (thru the screen) and then rotate the output shaft while holding the oil pump body. Do this several times until oil can be seen pulsating just under the screen which will indicate that the oil pump is functioning.
16) Install the input shaft assembly in the bearing housing.
17) Place the shaft sealing spacer over the pulley end of the input shaft and push it down into position under the shaft seal.
1) Oil all moving parts with Type “A” automatic transmission fluid.
2) Install the bearing housing onto the scroll housing and secure it with six hex head capscrews, lockwashers, and flat washers. The capscrews should be tightened to 100 inch/pounds. NOTE: The flat washers should be placed under the lockwashers to prevent gouging of the housing. CAUTION: Tighten the bearing housing down evenly to prevent loss of concentricity between the drive system and the housing assemblies.
1) Position the thrust bearing onto the rear of the sliding flange of the variable-ratio pulley.
2) Insert the special washer into the rear of the front (fixed) flange of the pulley. NOTE: The chamfered inner edge of the special washer should face the rear of the pulley flange.
3) Press the splined pulley hub into place in the front (fixed) flange of the pulley.
4) Position the sliding flange of the pulley to the splined hub. NOTE: The sliding flange should fit the splines but slide easily. If it fails to do so check for burrs on the splines.
5) Slide the key into the keyway of the input shaft (the key should slide easily in the groove and not have to be forced).
6) Push the variable-ratio pulley assembly down into position on the end of the input shaft, and secure with the retainer, lockwasher and socket, or hex head capscrew. Tighten to 200 inch/pounds torque.
7) Remove the supercharger from the special holding fixture, and remove the scroll cover from the scroll housing so that the impeller can be installed.
The impeller should be fitted to the output shaft to show an approximate clearance of 0.012 inch between the rear of the impeller and the face of the diffusor section. Shims of varying thickness were used to readily accomplish this clearance.
1) Wipe the face of the diffusor to free it of any foreign material, and then measure the depth of the face of the output shaft below the face of the diffusor. Take several readings to determine the exact, existing depth. Once this figure is obtained, 0.012 inch should be added to it as a basis for selection of shim, or shims. EXAMPLE: The surface of the output shaft is determined 0.015 inch below the face of the diffusor section. When 0.012 inch is added (for clearance between the impeller and the diffusor face), it is seen that a shim 0.027 inch thick (0.026 to 0.028 inch is acceptable) is required.
2) After determining the depth and correct shim, or shims, to use, the impellor and shims are assembled to the boss of the output shaft. Secure with a flat washer, lockwasher, and hex head capscrew tightened to 200 inch/pounds torque.
3) Use a feeler gauge to check the clearance between the impellor and diffusor face at several points around the impellor. The allowable tolerance of clearance is: 0.009 inch – GO; 0.015 inch – NO GO. If the allowable tolerances are not obtained, the impeller will have to be removed and the shim, or shims, refitted. CAUTION: Before measuring the face depth of the output shaft, the supercharger must be assembled and all retaining screws between the bearing housing and scroll housing tightened to 100 inch/pounds torque. The impeller retaining screw must be tightened down to 200 inch/pounds torque before measuring for allowable tolerances. Use special tool ST-103 to hold the impeller whilst tightening.
4) Assemble the scroll cover to the scroll housing and tighten the retaining screws securely. A flat washer should be used between each lockwasher and the surface of the cover to prevent gouging.
1) Rotate the input pulley several times to insure that there is no internal binding and that the impeller is not dragging against either the diffusor face or the scroll cover. During this check the pulley should turn rather hard, but should nether grab nor ratchet while being turned.
2) Check that the sliding sheave moves freely along it’s
3) After the supercharger is assembled to the mounting bracket, the oil sump should be filled with 8 ounces of Type “A” automatic transmission fluid. It is recommended that the input pulley be turned rapidly at least 12 revolutions, after the lubricant is added, to prime the oil pump. This will prevent the possibility of a “dry” start.
I’ve attached scans of the special tools, as recommended by McCulloch, required to conduct a rebuild of a VS57 supercharger. As can be seen from the diagram these tools are easily made up, and are straightforward to use. Alternative tools are used in the disassembly and re-assembly photographs and these are discussed where appropriate.
This is basically used as a jig to place the ball driver on when pressing a new bearing onto the input shaft, thus preventing damage to the ball driver surfaces. McCulloch recommended using an old input shaft, however these are not readily available so a feasible alternative could perhaps be turned up on a lathe.
ST-101 and ST-102
Basically steel tubing with the dimensions as specified in the diagram. These are used for pressing the bearings onto the input shaft and for pressing the seal onto the input shaft.
This is has dual functionality in that it is used to hold the impellor whilst undoing the impellor retaining capscrew, and it is used to hold the variable ratio pulley whilst removing the pulley retaining capscrew. An alternative that could be used whilst removing the impellor could be a triangular piece of metal or wood, screwed to the scroll housing edge, as shown in one of the disassembly photos. Once thing to be aware of though is that it is critical that the impellor should not be damaged during removal (or installation!), so tread carefully when attempting to remove it. Any damage to the impellor will cause it to become unbalanced, with catastrophic failure extremely likely at higher RPM’s. When removing the variable ratio pulley, a viable alternative is to use an old drive belt to prevent the pulley from rotating, as shown in the first disassembly photo.
This is essential for removing the impellor and should be made up as specified in the diagram. It is inserted into the bolt hole left after the impellor retaining capscrew has been removed, and turned clockwise so that the thread catches on the impellor, and pulls the impellor from its shaft without damage.
This is basically a leverage button used when removing the ball races from the race load assembly and the scroll housing. When placed on the ball race it protects the ball race surface whilst levering out the ball race using two screwdrivers. Anything that can be used as a leverage point, and that protects the ball race, can be used in its place.
This is used during bearing removal from the input shaft. It provides straight edges used to support the input shaft bearings allowing the input shaft to be pressed out of the bearings using an arbor press. Personally I think that it would be more appropriate, and invoke less risk of damage to the input shaft, if a bearing puller was used instead, as shown in the disassembly photographs.
This is the jig recommended by McCulloch which should be used whilst disassembling and reassembling the supercharger. It’s purpose is to provide a secure base for dismantling and assembly, without their being risk of damage to the supercharger. Please bear this in mind as you wrestle with your supercharger in your vice or on your workbench.