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Old 07-20-2020, 10:27 PM   #18
Don Rogers
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Join Date: May 2010
Location: Wildwood, MO. (near St. Louis)
Posts: 1,499
Default Re: 1936 aluminum heads dome/no dome

frnkeore...The "40" prefix head came out in 1933 as an aluminum head with 18mm spark plug threads. In 1934, "A" was added to the part number as a suffix to distinguish the aluminum head from the cast iron "B" head. In July 1935 a new designed "A-2" head was introduced necessitating that the original "A" head suffix be changed to "A1". Both "A-1" and "A-2" heads were used thru the end of 1936 production.

Here are some photos showing differences between the "A-1" and "A-2" heads as well as the domed "48" head.
Attached Images
File Type: jpg Head Compare small.jpg (48.1 KB, 34 views)
File Type: jpg ALHEAD_2.jpg (49.9 KB, 28 views)
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