With all the case machining done, the next step is setting the rotor to case wall clearance at the bottom, and at the sides. I set the bottom clearance at .006 at each corner. The clearance between the side wall of the case, and the tip of the rotors will not be set at a specific number, rather it will be set to equalize the clearance on each side. In short, the goal is to have the rotors centered in the case, left to right. Similarly, the top clearance is not something that can be changed, as the rotors are of a fixed diameter, and tightening the bottom clearance loosens the top clearance, of course. The bottom clearance is the most important though, as this is what keeps the boost in the intake manifold from leaking back around the tips of the rotors. Once the case wall to rotor clearances are established, these clearances are locked in place with a new set of slightly oversize dowel pins, that precisely preserve the position of the end plates in relation to the case. Re-doweling the case will be covered in the next video, Video 13.
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Disclaimer: This video series is not intended to be an exhaustive “How to do it” tutorial on how to rebuild a 6-71 blower for Gasoline use. Rather, it is meant to be a “How I did it” journal of one of many projects that I undertake in my home workshop, using hobbyist equipment and methods. If you attempt to duplicate any of these methods, you do so at your own risk. Therefore, I will not be held liable for any incidental or consequential damages as a result of trying to duplicate these methods.

Sources for clearances and tear down/assembly details referenced the Detroit Diesel assembly manual, with additional details referenced from the SA Design book “A Do-it-yourself guide to: Street Supercharging” by Pat Ganahl, ISBN 0-931472-17-2. If you are not an experienced mechanic/machinist, do not attempt to replicate this work. Take your Blower to a professional Blower builder.