Hercules Model SK
'Is $650 too much to pay for a 2-1/2 HP Hercules Model SK engine?' That was the way a conversation started with Rex Pyles at the recent gas engine show in Portland, Ind. My reply was to the effect that you probably won't have another chance to get one, because I have only seen one other. About a half an hour later, Rex came by again and said he was able to get it for $600. He brought it by later on his way over to his exhibit trailer. It is engine number 369868, manufactured in 1928.
The normal 2-1/2 HP Model S is unique in a couple of ways. First, it is a departure from the normal Hercules engine design in that the valves are side by side, rather than above and below, in the head. To accommodate this valve arrangement, the rocker arm is set at a slant. The crankcase area has no cast bottom and the fuel spout comes either out of the front or rear of the base.
Secondly, the 2-1/2 HP Model SK is unique because it is a throttling governed kerosene engine, yet it still has the open crankcase and spoke flywheel design. The 2-1/2 HP Model SK and the smaller 1-3/4 HP SK were in production in 1928 and 1929. Interestingly, when Hercules offered these engines they also offered the newer three-hole flywheel Model XK throttling-governed engines in 1-3/4, 2-1/2 and 3-1/2 HP sizes. Sears only offered the XK models at this time.
The governor mechanism was modified, with an arm going into a hole in the side of the block with a rod to the throttle butterfly running along and on top of the fuel tank and coming out a hole in the front of the base. Most of the later engines of these sizes had the governor arm hole cast into the base, even though the vast majority of the S models at this time were still hit-and-miss governed.
The production run on the 2-1/2 HP SK Hercules lasted about a year and a half. I would guess fewer than 300 were ever built.
Glenn Karch is a noted authority on Hercules engines. Contact him at: 20601 Old State Rd., Haubstadt, IN 47639, or e-mail at:firstname.lastname@example.org