Howdy all,
 As others have noted, this is a flat head three cylinder engine head which probably dates from around the 1930s or 1940s although it could be newer than that. Stylistically, the angular shape of the head also helps date this item within the 1930s or 1940s. If you take the diameter of the combustion chamber (the round semi-circles) that will give you a rough estimation of the engine bore. 
 Off hand, I would take a guess this was off of some sort of pony-motor which was the preferred method for starting larger diesel engines prior to the advent of reliable electric starters for high compression engines. Industrial diesel engines were used in everything from crawlers (bull-dozers or other "tracked" vehicles), road graders, stationary electrical generators, large logging trucks, yarding engines (for loading logs), donkey engines (for skidding logs out of the woods), hoists, etc. These diesel engines were not huge, but their high compression rating made it very difficult to spin the engine over fast enough for the diesel fuel to ignite due to the heat generated by compressing the fuel/air mixture. 
 A pony-motor is a small gasoline engine (2-3 cylinders) which was rigidly mounted on the larger diesel engine. One would start the pony-motor, allow it to run about 10 minutes to heat the cooling water for both engines, and then manually engage a clutch which would spin over the diesel engine with enough speed and torque to start it. Following this, the pony-motor would be shut down and not used until the diesel needed to be restarted. These pony-motors were always flat head engines, had very small displacements, and usually were incredibly simple engines since they were not designed for any real performance. The small water jacket on this head, taken with its small size inlet all indicate minimal duration to its operation and limited horsepower. 
 If there was ever any equipment or stationary engines of around 200 - 500 horsepower this very well might have been associated it was diesel powered. I would also note that these horsepower ratings might seem low, but industrial horsepower is rated using a slightly different system than automobile horsepower today. I hope that this is of some help, and if you have any questions I would be happy to help you. 
 
 Stathi 
    ______________________________________________________
 
 Efstathios I. Pappas, MS
 Doctoral Student
 Department of Anthropology/096
 University of Nevada, Reno
 Reno, NV 89557
 (775) 323-5730   
 -----Original Message-----
 From: [log in to unmask]
 To: [log in to unmask]
 Sent: Tue, 3 Oct 2006 4:06 PM
 Subject: Machine Part ID?
 
  Hello Histarch-ers, 
 
 I'm inspired by all the industrial machine/process expertise we evidently have on this list to make an appeal for help in identifying an artifact found this summer at my ca. 1885-1935 dissertation research site in Tulare Co., California: It's a cast iron object which looks like some sort of cylinder head, and measures very roughly 10" x 6" x 1.5". The number on the top view is "6251[?]1-4." 
 
 Pictures here: 
 https://webfiles.berkeley.edu/stacyk/public_html/Machine_Part.jpg 
 
 Any ideas on what kind of engine/machine this may be from? 
 
 Thanks! 
 Stacy Kozakavich 
 
 Ph.D. Candidate 
 Department of Anthropology 
 University of California, Berkeley 
   
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