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Supercharger facts or myths?

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  • Fuel System: Supercharger facts or myths?

    Be sure to store in position it runs on engine? Why?
    I have heard many other things said about the VS and SN series. Some make sense. Others, I don't know.
    After talking to Mr Erb, I seemed to gain a little better understanding. There are so many voodoo rituals attached from hear say, that I only go in the area where mine is stored on a full moon night and stand on one foot and wear sterile gloves to even touch it. Seriously, some of you that know these thigs tell the rest of us about them. I understand that just storing a rebuilt unit for a long time will result in ( some long metalergical word) that causes you to need to replace the 5 big balls and races. I can understand this. I understand you can't see it with the naked eye. Anybody here really know the quirks or "refreshing" and "rebuilding" that care to share?

  • #2
    Sure, the word is oxidation. Rust will pit those little balls, and wear things out in short order. The shop manual advises using gloves to handle them, as skin oils and acids will start the corrosion process. The outer races, and output shaft must be in perfect shape too with no wear, pits or scratches.
    When rebuilding one, it's imperative that hospital room cleanliness is adhered to.
    The race tension springs must be of equal tension, but , also at the same length. The scroll housing often has grooves worn where the labyrinth piston ring type seals are. (a speedy sleeve will fix that). The impeller spins extremely fast, and any corrosion, chips,or cracks will cause destructive forces. If in doubt replace it.
    NOS impellers (and original) were magnesium. New ones are aluminum. The magnesium ones don't create as much inertial forces.Set the impeller to scroll housing clearance with shims, the closer to the housing the greater the output. Allow for temp expansion. Don't drop the unit on the end. The scroll cover is very flat and can bend if hit too hard. The pulley end will transfer forces to the driver and drive balls, and create flat spots. We are talking about tolerances of .000001. The input shaft bearings also cant have wear or radial runout.
    The oil pump bushing is NLA, but if it's in good shape you can re-use it. The pump spring should be replaced regardless. If the bushing is worn, new pumps are available and you replace the whole unit. There is no bushing in the new ones and the shaft rides in the aluminum bore. The good side is that the plunger of the pump is larger diameter, and it puts out more volume and pressure. The Ball driver on originals are aluminum, and the securing screws can work loose, and corrosion can set up between the steel balls and the driver. Aluminum oxide will ruin the balls and scratch the heck out of them. New ones in bronze are much better. Don't skimp on the balls themselves. There are differing quality sets out there. Get the ones from later series Paxtons as quality control was not as good on the McCulloch drive balls. When Andy took over Paxton, he sourced quality parts from Europe that had much, much closer tolerances. If you refinish the outer case, don't get ANY overspray on the inside. Use B&M non synthetic transmission fluid. Change it every 3000 miles. Torque the case bolts like you would a wheel, in alternating patterns to prevent case distortion. Don't "blip" the throttle as the drive balls will slip and flat spot. Don't run with the outlet hose disconnected, as the impeller will also over speed the balls and flat spot them, it needs the boost force to preload it.
    If you can do all these things you will not have problems.
    Bez Auto Alchemy
    573-318-8948
    http://bezautoalchemy.com


    "Don't believe every internet quote" Abe Lincoln

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    • #3
      Storing a supercharger is always bad science. They require frequent 5,000 RPM shifts to prevent deterioration.

      jack vines
      PackardV8

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      • #4
        So, if I understand right, the spare chargers when new were in danger after a days or weeks. What about the new cars that didn't sell for a while? What about the one the guy from Georgia has for sale on the forum now? Would it be a good idea to take the pressure off the unit by loosening screws and letting the bodys back apart?

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        • #5
          No, I was saying when (if) dropped on the nose.....sorry for the confusion.
          Bez Auto Alchemy
          573-318-8948
          http://bezautoalchemy.com


          "Don't believe every internet quote" Abe Lincoln

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          • #6
            Sorry Brad, I wasn't saying you confused me. I really appreciate the time you took to explain. I guess the storing part of these units is the one thing that so many people seem to diagree on. Not me! cause I don't know enough to disagree. lol

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            • #7
              Before placing a used Paxton-McCulloch supercharger into storage, the case should be opened up, and the internals thoroughly flushed out with regular ATF, then re-assembled and stored in the 'installed on engine' position with new ATF added, and brought up to the normal (full) level. Store in a dry an area as possible, and remember to spin unit in direction of normal rotation a few times a year. It will last for longer than You'll ever need it!

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