I saw this picture on the web. It says 1910. Do they have the date correct? If you zoom in on the second motor it looks to have valve covers. The engines appear to be painted black. The intakes look like they could be aluminum, but not the dog-leg style. I'm sure somebody has seen and knows more about this picture. I always like the old factory pictures but I think it is later than 1910.
I think you're right
This image was first published in a series of articles that appeared in 1914 and 1915 issues of "The Engineering Magazine", which were authored by well-known automotive journalist Horace Lucian Arnold. All of Mr. Arnold's articles were republished by the Engineering Magazine in 1915 under the title "The Ford Methods and the Ford Shops".
When the work was about 75% complete, Mr. Arnold died unexpectedly. In order to complete the work, The Engineering Magazine brought in another journalist named Fay Leone Faurote. Mr. Faurote took up where Mr. Arnold left off, and fished the work almost seamlessly. "The Ford Methods and the Ford Shops" lists both Horace Lucian Arnold and Fay Leone Faurote as its authors, although Mr Faurote gave most of the credit to Mr. Arnold.
This particular photo appears in Chapter V "The Motor-Test Blocks and Chasdis Assembly Line", near the beginning of the chapter.