The compression ratio of this engine was lowered by almost 20 percent from that of the vertical 4. This, in combination with the low bore-to-stroke ratio, the unheated charge, and the later mechanically operated inlet valve, indicates that the Wrights were now attempting for the first time to secure from an engine something approaching the maximum output of which it was capable.
As the engine originally came out, it continued to utilize only one spark plug in each cylinder. The high-tension magneto had a wide range of spark advance adjustment, which again provided the only control of the engine when equipped with the original fuel pump injection.
The location of the valves and pushrods was similar to that in the 4, so that the cams were immediately adjacent to the camshaft bearings, which were carried in the crankcase ends and in the heavy webs. The camshaft was gear-driven and the cam shape was similar to that of the last 4s, with a quite rapid opening and closing and a long dwell, leaving the valve opening accelerations and seating velocities still quite high.
The crankshaft was a continuation of their basic design of rather light construction, particularly in the webs. The cheeks were even thinner (by 1/4 in.) than those of the 4 although the width was increased by 1/8 in. (see Figure 13e). For the first time they went to a forging, the rough contour type of the time, and utilized a chrome-nickel alloy steel.
Lubrication was by means of the usual gear pump, and the piston and rod bearings continued to be splash-fed. The rod big-end bearing carried a small sharp undrilled boss at the point where, on the other engines, had been located scuppers whose purpose was apparently still to throw lubricating oil on the cylinder wall carrying the more highly loaded side of the piston. The rod big-end bearing was lubricated by a hole on the top of the big-end boss catching some of the crankcase splash, which was then carried to the bearing by a groove.
When the 6-cylinder engine was completely redesigned in 1913 this led to the introduction in late fall of that year of a new model called the 6-60, the 60 designating the rating in horsepower. There is little in the Wright records to show why such a radical revision was thought necessary, but the general history of the period gives a rather clear indication. The competition had caught up to the Wrights in powerplants. Other engines were being installed in Wright airplanes, and Navy log books show these other engines being used interchangeably with those of the Wrights.