Little Giant

Chain-driven Overhead Cam Engine is Long on Features but Short on History

| April 2005

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    David Williams’ Little Giant after restoration and as found. Note the 2-foot carpenter’s square, which gives some scale to the engine.
  • 04-05-018-Williams-5.jpg
    A close look at the overhead camshaft, ignition timer and rocker arm, which are carried in a common bracket. The bracket can be adjusted fore and aft to take up slack in the cam chain. The device on top of the cylinder and to the rear is the vacuum pump.
  • 04-05-018-Williams-8.jpg
    The disassembled engine shows the 10-inch-long, 3-1/4-inch-diameter piston incorporating a 5-inch center for the vacuum pump. Note the stepped base casting.
  • 04-05-018-Williams-3.jpg
    Except for the camshaft, all the ancillary parts on the front of David’s engine are made from brass.

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  • 04-05-018-Williams-5.jpg
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I've been collecting engines since 1971, and I have hunted down engines across Ohio, Pennsylvania and New York. In February 2003, I saw an advertisement for an estate auction only 13 miles from my home. The advertisement listed an old engine. The day of the sale it was 15 degrees F outside and there was 4 inches of snow on the ground. The engine was very rusty, but I bought it anyway. When I paid the auctioneer's secretary, who I graduated from high school with, I said, "What will I say to my wife?"

Little Engine, Big Details

This little engine uses a block-type skip chain driving an overhead camshaft that operates the exhaust valve and the ignition timer. The engine appears to be of 1905-1910 vintage; the block-type skip chain (called a "skip" chain because it doesn't ride on every tooth) disappeared from use about this time. It also uses an odd Lunkenheimer carburetor.

It has make-and-break points inside the timer cover and a buzz coil to the plug. The entire front mechanism, including camshaft, rocker arm and timer, is mounted on a bracket that can be moved to tension the chain. There are guides under the bracket that allow the camshaft and everything else to be adjusted back and forth, and not tip, tilt or cock in any way while being moved. The carburetor, timing lever, timer, overhead cam, exhaust rocker arm and all adjustment pieces are made from brass.

It has a round, hollow piston rod with a brass flip-up oiler set in the rod to lubricate the wrist pin and rod bearing (the oil passes through the hollow rod), which is brass molded to the round steel rod. At 0.775", the wrist pin is an odd diameter, as a standard size would be 0.750", or 3/4-inch. It uses a single piece of 1-inch pipe for its thermo-siphon, tank-cooled system. The original water hopper is gone. The one on it is an old tank I found that has, to my eye, the right patina.

The engine base is stepped several times; it's wide at the front and narrows between the flywheels. Its odd-looking piston is 10-1/4 inches long, with a raised, 5-inch area for the integrated vacuum pump. The pump and piston create the vacuum, with pump timing controlled by the chain drive.

I have seen another engine like mine with the same base and main castings, but it has larger, wider and heavier flywheels, and a Scheibler carburetor. Another collector found a similar engine in New York with the same base. It's also an overhead cam design and chain-driven, but otherwise looks different all around. Also, on my engine where the 1/2-inch pipe threads into the head for carburetor intake, the casting is almost flat, but the other two engines have a large, protruding boss. Was the casting changed to hold the larger and heavier Scheibler carburetor? None of the engines feature a governor to control speed.


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