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THE effect of the aircraft-engine intake system on the design of other engine components is here related by Mr. Doman, who applies his findings particularly to a series of 4¼ x 3½ horizontally opposed aircooled engines. Valve sizes were varied to obtain the maximum size of inlet valve without appreciable restriction of the flow through the exhaust valve, and at the same time that would provide a strong bridge in the cylinder head between the valve openings. Care must be taken that restrictions to flow are not created in the intake port. “The intake port,” Mr. Doman says, “is probably the most critical item in the whole induction system as far as affecting power output.”

THIS paper discusses the parallel design and development work of two air-cooled engines with widely different applications, although the basic design of both engines is quite similar. Instead of following the usual aircraft practice in any detail, the author points out the advisability of using automotive practice and thus bringing about a simplicity in design which is impossible when following the normal aircraft practice. The cylinder design of the two engines is discussed and points of similarity shown. A description is given of an 80-hp, 176 cu in. aircraft engine, and the reasons why the design for this particular engine was selected over five other types which were designed, are given. It is pointed out that the use of large-production automotive equipment such as starters and generators in light plane engines effects economies which can never be expected by using the more specialized apparatus which is available for airplane engines only.