TROUBLESHOOTING THE GAS ENGINE


| May/June 1967



Two Fordson tractors

Courtesy of Everett R. Shreeve, Salamonia, Indiana

Everett R. Shreeve

Star Rte. 2, Gunnison, Colorado 81230

On page 32 of the Mar-Apr 1967 GEM, Fred Gertje of Orofino, Idaho, inquired as to the identify a certain engine he had. The best clue I found as to its identify was 'valve in head with a post between the valves with a spring on it and a plate that connects the post with the two valves.' The only engines I have seen with this arrangement are Hercules built, and since it was painted red I would conclude that it is probably the Economy engine built for Sears Roebuck by Hercules. All other parts of Fred's description compared to this engine except the water jacket and cylinder being cast together. On a 5 HP engine this should have been two pieces, the hopper being removable. Further correspondence with Fred revealed that it was. One of the slight differences I have noted between the Economy and Hercules engines is the square cornered hopper of the Economy, the Hercules having fairly rounded corners.

The drag, or automatic poppet valve on the intake worked fairly well with slow speed engines but had some drawbacks. The fuel-air mixture enters the cylinder when the downward movement of the piston causes the outside air pressure to exceed the internal pressure and pushes the valve open. However, as the piston reverses direction and starts its compression stroke, the intake air is still flowing into the engine. The sudden reversal of flow causes some of the mixture to reverse and escape before the valve can close. Then the valve shuts so hard it tends to bounce and reopen, losing more of the mixture. This could be prevented by using a stiffer spring, but this would prevent the valve opening soon enough on the intake stroke.

The design and tension of the intake valve spring is quite critical to proper operation of the engine. The spring should not increase rapidly in tension as it is compressed, so it should have as many turns as possible without interfering with the maximum opening movement of the valve. If an intake valve spring must be replaced it should compare as nearly as possible to the original. If this is not possible, a trial and error method must be used.

This is the picture of my display which I took four places this past summer. Two Fordson tractors, one 1927 and one 1926 and 6 gas engines, one 1? H.P. 1922 Hercules, one 1? H.P. 1922 John Deere, one 6 H.P. Fairbanks Morse 1917, one 1? H.P. 1934 single flywheel McCormick Deering, one 1? H.P. 1933 Fairbanks Morse single flywheel, one Maytag single cylinder and one 850 Dulso light plant. I belong to the Tri-State Gas Engine and Tractor Club of this area.

One method is to use a lighter, longer spring than the original and, using washers to increase the tension, adjust until satisfactory operation of the engine is reached. Satisfactory being the smoothest operation at the rated RPM with the least fuel setting. The tension can then be measured with a small spring scale and a spring of the proper size and shape and tension can be made or, hopefully, found.