Beginning in 1921, the Hercules Gas Engine Co. introduced what I would call sort of an oddball engine. It featured a one-piece block with a 3-5/8-inch bore. When introduced, it was rated at 2 HP in the Hercules, Jaeger and Economy brands. From the very beginning, the ARCO brand was rated at 2-1/2 HP. Photo 1 shows an early one with a dry four-bolt head. Interestingly, it has a larger-than-normal Webster magneto, which means it has the seldom seen 303K32 bracket. Two other obvious features are the slanted rocker arm and the side exhaust.
On some of the earlier engines, there is another unusual feature. The spindle for the governor shaft is cast as an integral part of the engine base (Photo 2). This means it takes a special governor bracket rather than the more common one that this size engine shares with the smaller engines. If you look closely in the photo, you can see the spindle between the flywheel and the hopper. Another oddity is the oiler pipe location. It seems to be just stuck in behind the hopper (Photo 3).
The Jaeger engine shown in Photo 4 is a more typical example of this size engine, with the four-bolt wet head and side exhaust, slanted rocker arm, oiler through the hopper and Wico EK magneto. The fuel spout position can be seen on the front of the base. There is another a fuel tank spout at the rear of the base.
The last example shown is the seldom seen throttle-governed kerosene version with the fuel mixer sticking out from under the head (Photo 5).
Somewhere along the line the engine's horsepower rating was increased from 2 HP. Both the Hercules and Jaeger brands were increased to 2-1/2 HP and the Economy brand was increased to 2-1/4 HP. Why was the Economy brand only re-rated to 2-1/4 HP instead of 2-1/2? I suspect it was done to avoid confusion with the earlier 2-1/2 HP Economy Model E engines.
Some people ask, "Are these engines rare?" The answer is no, they really aren't rare, but rather, just odd. However, within this group, those with the dry head, spindle on the block, oiler behind the hopper or kerosene mixer are rarer.
Glenn Karch is a noted authority on Hercules engines. Contact him at: 20601 Old State Road, Haubstadt, IN 47639; firstname.lastname@example.org