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http://books.google.com/books?id=52WIEG-1TjgC&pg=PA189&lpg=PA189&dq=xm656+engine&source=bl&ots=qTnOGmc8rA&sig=OV3VNBtz4VOBLLEijwmi0QJO-7o&hl=en&sa=X&ei=cJHMUsuMMYT1qwGF1IHgAQ&ved=0CDsQ6AEwAg#v=onepage&q=xm656%20engine&f=false
It's the LDS 465-2.