Hercules Engine News

Unraveling Production Dates

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There are many mysteries surrounding the production of Hercules-built engines. Slowly, some of these mysteries are being unraveled.

Several years ago a chart was developed to aid in determining when a particular engine was most likely built. Many of you are probably familiar with that chart, but arriving at an exact date is very elusive even if you have the original records.

First, there is the production of the various parts that make up a complete engine, the production of which could easily be spread over several months. Beginning in late 1924, many engines had one or more parts with casting dates on them. Often times the casting date order does not follow the serial number order very well.

Second, several months could pass before all the parts were finally assembled into a complete engine. From there, the engine was tested, painted and, finally, a serial number tag was applied from a supply that had already been numbered.

Third, the engines were then shipped by rail to warehouses, dealers or individual purchasers. And even though a certificate was issued to the eventual owner, it could be dated quite sometime after the engine was actually built.

To complicate the dating issue a little more, series of tags from a supply already numbered were stamped up for each sized engine group listing the horsepower, model and rpm. With data from nearly 4,000 of these engines now on hand, these blocks of serial numbers become evident when all known numbers are listed chronologically. Table 1, taken from a segment of the list of currently known engines, is a good illustration of this.


Currently Known Engine Serial Numbers and Engine Size

Serial Number


93,247 to 97,770

1-1/2 HP

97,989 to 101,141

2-1/2 to 3 HP

101,292 to 103,285

5 HP

103,300 to 104,342

7 HP (most are 1916)

104,849 to 104,947

9 HP

105,051 to 105,625

12 HP

106,302 to 117,570

1-1/2 HP

117,747 to 120,046

2-1/2 to 3 HP

120,556 to 122,976

5 HP

123,303 to 124,642

7 HP (most are 1917)

124,728 to 124,884

9 HP

125,312 to 125,458

12 HP

125,945 to 132,339

1-1/2 HP

132,636 to 135,739

2-1/2 to 3 HP

135,940 to 137,800

5 HP

137,842 to 139,330

7 HP (most are 1918)

139,522 to 139,959

9 HP

140,100 to 140,507

12 HP

By studying these serial numbers, we can begin to get a rough idea of the production of each size of engine offered. It would appear that out of these groups shown here about 24,000 (49 percent) were 1-1/2 HP; 9,500 (20 percent) were 2-1/2 HP to 3 HP; 7,100 (15 percent) were 5 HP; 4,500 (9 percent) were 7 HP; 1,500 (3 percent) were 9 HP; and 1,500 (3 percent) were 12 HP. Yes, I know 1 percent is missing somewhere.

It is also very possible as you study the listings that, for example, 1-1/2 HP engine number 125,945 could have been built on the same day as 12 HP engine number 140,100.

I am sure that these serial number/horsepower sequences are not perfect and leave a little to guesstimating, and there appears to be the possibility that a few engines of one size may have serial numbers co-mingled with another size.

As a side note, there were many responses to the article on the Model XK Hercules and Economy engines (GEM, June 2002). Many more X Model engines and their casting dates have now been added to the list.

Glenn Karch is a noted authority on Hercules engines. Contact him at: 20601 Old State Road., Haubstadt, IN 47639, or e-mail at: glenn.karch@gte.net