According to the Miller data plate on the engine, its spec's are:
In Mark Dees' book, “The Miller Dynasty,” Chapter 53 addresses the Miller 151/200/220 four-cylinder racing engine. In summary:
Miller and Goossen began working on this engine in late 1930. Although Miller wasn't particularly interested in four-cylinder engines at the time, it was obvious there was a need for a new and more powerful short track engine that people could afford -- not the average guy, certainly, but the various top hands at Ascot Park and the better circuits in the East and Midwest. The new engine would need to be at least 200 CID to give it punch off the turns equal to the various Ford Model A conversions. The same basic design could probably also be built as a new contender for the 151-c.i. hydroplane classes.
The new engine was a logical development of the well-tried 151-c.i. Marine engine. Overall cylinder block length of both the 151 and the new 200/151 was 19 inches, but little or nothing actually interchanged between the two. The new engine used four valves in a pent-roof chamber, as was done with the Miller 183 of 1921. For no good reason, the first few engines were designed with downdraft intake ports (and ours is one of those). To accommodate for the spark plug cups, coolant passages and ports in the limited volume of space between the cam towers, adjacent intake passages were joined together, or “siamesed,” as Miller had done with the 230 and the 303 (and our own V-16 and V-8). This intake port design causes one cylinder to rob another and has a nasty effect on the engine's torque characteristics, even more in a four than in eights and sixteens.
Soon after the engines were introduced, because of the threat of the bored-out 214 CID D.O. Cragar Fords, the bore of most of the Miller 200s was taken out from 3.875” to 4.0025”, giving 220 CID.
The first examples of the new 200, at $2750 each, went to car owners Bill White, Art Sparks, Danny de Paolo (Pete's brother), Shorty Cantlon, Doug Harrison and probably a few others. Sparks and Paul Weirick used theirs to replace the D.O. Cragar in their Ascot car driven by Stubby Stubblefield, but weren't completely happy with it.
Acting on advice from Drs. Patchett and Reid of Stanford University, who were doing flow bench work, Sparks cast new blocks which used four oval sidedraft intake ports. The porting change really woke the engine up, and soon Bill White went to Miller for a similar block for his Acsot car which Ernie Triplett had been driving in the latter part of the 1931 season.
Thus was born the Miller 220 later the Offy 220, the sweetest, most dependable of all the Miller Fours. The Miller 220 is the engine Fred Offenhauser continued to build and update (with the invaluable assistance of Leo Goossen) after Miller’s bankruptcy in 1933.
Could the Museum's engine actually be one of the “new” marine engines? Probably not. There is no mention in the Dees book of a marine four of this design being built other than the earlier 151, and ours is (at least according to the data plate) a 200. Therefore, our engine was likely built as a race car engine, probably early 1931.
We don't know if our engine is still at 200 CID, or was at some time bored out to 220, but it is obviously the early 200 design with downdraft porting. Its magneto drive setup is typical for the early engines. Dees noted that gears in the magneto side-drive were more reliable than the bevel gears in the front-mounted angle drive used on later engines, but the side-drive mag (like ours) tended to get in the way of the manifolding on the side-port 220s.