In Reply to: Re: timing gear cover question? posted by Randy(PA) on October 21, 2018 at 23:50:35:
Here’s what I found last night, I got out my May, 1950 MPC and discovered some interesting facts. I need to delve deeper but the front cover may have been cast iron. The ’50 MPC shows the 9N-6019-B, used 39-50, no mat’l spec listed but then they hardly ever do, that’s an EI sheet fact and defined in p/n suffix. Then it has 8N-6019-A –Cast Iron AFTER s/n 263843 –just like I called it, when the side mount distributor was added. P/N 8N-6019-B, aluminum, used ’50. The MPC also lists 8N-6017-A, cast iron, and 8N-6017-B, aluminum being used in ’50. In the May, 1949 MPC, the part list stops at p/n 9N-6018 on page 29, and the next p/n is 9N-6149-A on page 30. There’s no reference to the 6019 cover. I am looking at the pdf version on the web site so will have to look into my hard copy further –it may be shown in a different assembly.
I’m spitballin’ here, but I’d say the original 9N front cover, p/n 9N-6019-A, was cast iron. It was changed to aluminum before 1940, probably early ’39. The same with the original 9N distributor –it was also cast iron, very rare. Parts were being revamped fast and furious back then and many fell thru the cracks of parts books. The original 6-Loop Style rear rims are a perfect example. A few of us concur that some changes occurred when they switched from the aluminum hood to the steel hood, after the first 700-800 units, most likely when the loop rims were declared obsolete and replaced by the box, or Hat Rim. There has to be some major design change for having both a 9N part prefix and an 8N part prefix and has nothing to do with material specs. Front covers appear to be interchangeable. The side timing gear cover, shows p/n 9N-6017 as used from ’39 – ’50. Then the 8N –A and 8N - B units released in 1950 when the other changes were released, mainly when the side distributor was released and proofmeter added.