In Reply to: Re: Donaldson Air Cleaner Cup? posted by Tim Daley(MI) on June 10, 2017 at 17:03:24:
The -C1, -C2, C3 all used the 15degree 30 Minutes angled outlet tube, whereas the earlier 39's used the straight (horizontal) outlet tube and required the more complicated tube 9N-18215-A to transfer the air down to the carb. The drawings for -C1 and -C2 were released in October'39, so they may be more appropriately called "mid '39". I would think that most of the two and three digit serial numbers had the straight tube cleaner bodies.