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The 4AD is the most common Singer in the U.S. here is a variety of information on the 4AD also known at the SM1500 Roadster

For starters grab this PDF it is a copy of a Motor Trader article on maintenance of the 4AD, when I purchased my 4AD back in the 1974 it was the only manual I had and I got my car on the road with this article. (you will need Adobe Acrobat Reader for this)
Once you have the Acrobat Reader, you can look at the parts list we have for sale.