Eaton Blower/Supercharger Rebuild

There are many different opinions and views regarding how to modify the M-Series, roots type, superchargers made by Eaton. Both the M62 and M90 are at their peak efficiency levels from the factory but of course there are some small tweaks worth making. Although running a smaller pulley is the easiest way to generate more power with these units, it is also the easiest way to push the blower out of its efficiency range and produce gobs of heat. Heat, as you know, is the enemy of all F/I applications. Roots type superchargers, although extremely reliable, are the least efficient due to their drag on the engine by belt as well as their tendency to generate good amounts of heat in regards to the IAT (Intake Air Temperature).

When it comes to modification of these superchargers, the common areas of modification are:
Porting of the inlet portion of the housing.
Porting of the internal housing.
Porting of the outlet plate of the housing.
Porting or Plugging of the "holes" on the outlet plate.
Running a smaller pulley.
Heat reduction, supporting modifications.

The basic idea here is to increase CFM without raising IAT's. These basic principles can be carried over to any other application using an M-Series blower. It should be noted, that the M-series superchargers are effectively air pumps. They do not internally compress the air themselves, but push it into the lower intake manifold. It is in the lower intake manifold that positive pressure emerges. Most folks think Eaton's roots-type units are actually squeezing the air like a screw unit. This is not the truth. No air passes between the rotors, the air is guided by the rotors along the sides of the housing; hence, no internal compression of air.


It is not a good idea to remove too much material from any portion of the blower. Extreme porting of the blower will disrupt the air and will reduce efficiency greatly.

The inside of the housing can also be lightly ported to increase internal surface area. It is important to note, that internal porting of the rotor housing should be very minimal. Basically, remove any and all casting flashes and ensure complete symmetry while removing as little material as possible. Removing too much material will interfere with air flow and the functionality of the rotors.

As you can see, this unit has severe scratching but will clean up nicely with light porting.

A light porting of the inlet housing will help increase intake CFM of the pump. Typically, if a TB (throttle-body) upgrade is available, it helps to match the TB port size to the inlet port for a smooth intake of air with minimal disruption. Smoothing this opening up and enlarging it slightly will help introduce more air into the rotor housing which can then be "pushed" into the lower intake manifold.
The output plate at the base of the housing is what can be modified the most. This plate has one large triangular and two small oval passages in it. The large triangle is the passage that air is pushed through by the rotors to create a positive pressure in the lower intake manifold. This passage can be opened up slightly and smoothed out for best flow. Opening it up too much will also disrupt airflow. This is where the most porting can be performed on the blower.

We start by cleaning the unit in the solvent tank. All mating, sealing, and bearing surfaces are taped with heavy plastic tape, and the unit is sandblasted. Once on the mill we remove only enough material around the edges and surface of the bottom plate to remove the uneven casting marks, leaving a polished machined look.



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