FUEL SYSTEM INSTALLATION
Gasoline giving the best results with this equipment is as follows: Gravity 58-62 deg. Baume A. Initial boiling point—Richmond method—102° Fahr. Sulphur .014. Calorimetric bomb test 20610 B. T. U. per pound. If the gasoline tank is placed in the fuselage below the level of the carburetor, a hand pump must be used to maintain air pressure in gas tank to force the gasoline to the carburetor. After starting the engine the small auxiliary air pump upon the engine will maintain sufficient pressure. A-7a and A-5a engines are furnished with a new type auxiliary air pump. This should be frequently oiled and care taken so no grit or sand will enter which might lodge between the valve and its seat, which would make it fail to operate properly. An air relief valve is furnished with each engine. It should be screwed into the gas tank and properly regulated to maintain the pressure required. This is done by screwing the ratchet on top either up or down. If two tanks are used in a plane one should be installed in each tank. All air pump lines should be carefully gone over quite frequently to ascertain if they are tight. Check valves have to be placed in these lines. In some cases the gasoline tank is placed above the engine, allowing it to drain by gravity to the carburetor. When using this system there should be a drop of not less than two feet from the lowest portion of the gasoline tank to the upper part of the carburetor float chamber. Even this height might not be sufficient to maintain the proper volume of gasoline to the carburetor at high speeds. Air pressure is advised upon all tanks to insure the proper supply of gasoline. When using gravity feed without air pressure be sure to vent the tank to allow circulation of air. If gravity tank is used and the engine runs satisfactorily at low speeds but cuts out at high speeds the trouble is undoubtedly due to insufficient height of the tank above the carburetor. The tank should be raised or air pressure system used.
IGNITION SWITCHES
Two “DIXIE” switches are furnished with each engine. Both of these should be installed in the pilot’s seat, one controlling the R. H., and the other the L. H. magneto. By shorting either one or the other it can be quickly determined if both magnetos, with their respective spark-plugs, are working correctly. Care should be taken not to use spark-plugs having special extensions or long protruding points. Plugs giving best results are extremely small with short points.
WATER SYSTEMS
A temperature gauge should be installed in the water pipe, coming directly from the cylinder nearest the propeller (note illustration above). This instrument installed in the radiator cap has not always given satisfactory results. This is especially noticeable when the water in the radiator becomes low, not allowing it to touch the bulb on the moto-meter. For ordinary running, it should not indicate over 150 degrees Fahr. In climbing tests, however, a temperature of 160 degrees Fahr. can be maintained without any ill effects upon the engine. In case the engine becomes overheated, the indicator will register above 180 degrees Fahr., in which case it should be stopped immediately. Overheating is most generally caused by retarded spark, excessive carbon in the cylinders, insufficient lubrication, improperly timed valves, lack of water, clogging of water system in any way which would obstruct the free circulation of the water.
Overheating will cause the engine to knock, with possible damaging results. Suction pipes should be made out of thin tubing, and run within a quarter or an eighth of an inch of each other, so that when a hose is placed over the two, it will not be possible to suck together. This is often the case when a long rubber hose is used, which causes overheating. Radiators should be flushed out and cleaned thoroughly quite often. A dirty radiator may cause overheating.
When filling the radiator it is very important to remove the plug on top of the water pump until water appears. This is to avoid air pockets being formed in the circulating system, which might not only heat up the engine, but cause considerable damage. All water pump hoses and connections should be tightly taped and shellacked after the engine is properly installed in the plane. The greatest care should be taken when making engine installation not to use smaller inside diameter hose connection than water pump suction end casting. One inch and a quarter inside diameter should be used on A-7 and A-5 motors, while nothing less than one inch and a half inside diameter hose or tubing on all A-7a and A-5a engines. It is further important to have light spun tubing, void of any sharp turns, leads from pump to radiator and cylinder water outlet to radiator. In other words, the water circulation through the engine must be as little restricted as possible. Be sure no light hose is used, that will often suck together when engine is started. To thoroughly drain the water from the entire system, open the drain cock at the lowest side of the water pump.
PREPARATIONS TO START ENGINE
Always replenish gasoline tanks through a strainer which is clean. This strainer must catch all water and other impurities in the gasoline. Pour at least three gallons of fresh oil into the lower crank-case. Oil all rocker arms through oilers upon rocker arm housing caps. Be sure radiators are filled within one inch of the top.