My 6-71 Blower rebuild, Part 15: Custom machining a Magnesium carb adapter plate.

I actually completed the carb plate about a year ago, but wanted to complete the main blower rebuild videos first, so that people did not think that I was procrastinating so much that I would never finish the blower itself.

Years ago, I made another plate like this by hand, mostly on a drill press, from a very long piece of Magnesium. The plate was actually long enough to make two plates in case I messed up on the first. My first plate was a success, so I had enough stock left over to make another plate, at some point in the future. Fast forward about 25 years, and here we are, with another blower build needing a carb plate.

My last engine ran great with the thin 4-hole carb adapter plate on it, got very good gas mileage (11 mpg) for a blown Big Block and it kept the carburetors as low as possible. I used this project as a good learning opportunity to make a relatively complex part (complex for me) to machine on the Bridgeport CNC, to keep an early vintage look to the finished assembly. Although Blower Drive Service makes very nice parts, a modern cast plate with the “BDS” logo machined into it does not look vintage in any way. I made LOTS of mistakes in Fusion 360, as this was my first live part done in Fusion, but in the end I got everything figured out, and I understand the CAM section in Fusion, much better now. I really love the look of machined Magnesium, and yes, I will either have to polish it up after a few years, or just live with the tarnished surface that will accumulate on the plate after it slowly tries to consume itself as a result of contact with the atmosphere.

This plate was a very satisfying accomplishment, and I was very relieved to get to the finished part, without making any mistakes that would cause me to destroy my only piece of Magnesium stock.

Finally, Magnesium chips are VERY dangerous. Even as careful as I was, I still had a handful of chips that I absent mindedly put into a plastic garbage can after surfacing the plate. A few weeks later I was cutting off a piece of stock on the chop saw, and a single spark bounced over my shoulder and lit up the Magnesium in the plastic garbage can. I knew very well from past experience that you cannot extinguish a Magnesium fire with water, so I immediately grabbed the garbage can and ran it out the back door. Unfortunately, the bottom of the can burned through right before I cleared the carpet at the back door, leaving a small melted spot in the ugly brown carpet. Well, we should have put new carpet in this house 5 years ago anyway...
================================================
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.