AN AID TO ENGINE TESTING.
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A Rising and Falling Plunger that Indicates Piston Position.
AUU SEFL little contrivance, known as the Stevens timing tester has recently ijeen introduced by ;a New York firm, for which it is claimed that it tells, instantly and accurately, the firing order of any engine, the correct connection of ignition wires, if the spark is timed correctly, if the valves are properly timed, and if a piston is correctly situated for safely burning out the carbon. The tester enables the operator to judge the position of the piston when in compression, on dead centre ancl-at• the begin. lung of the firing stroke, as well as to test the sparking.
Formed after the mariner of a spark .plug, it. takes the place of a plug during the operation of testing, a quick hook-up connection for the wire being provided.. The tester consists of a carefully balanced plunger, having a pin with an indicator ball on top. This plunger rises and. falls with the compression in the cylinder, floating on the air from the cylinder and showing the slightest change in the piston position. The upper part of the tester, with its moulded insulated cap, is used as a spark plug terminal, and . by watching the movements of the indicator ball and the spark which passes between the terminal and the ball it is possible actually to judge the piston movement and to note
the exact period when the spark takes place, from which it is easy to tell with absolute certainty' whether the spark is early, late, or correctly timed, the col-rect time for sparking being, of course, at the moment when the piston reacheE the top of its stroke.
By testing the first two eylindergwith all other plugs disconnected—in a four-Cylinder engine, the order of firing tan be ascertained for all four cylinders, but with Six and eight-cylinder engines it will be necessary to test them all. Valve timing, too, is rendered ea-s-y and reduced to a certainty, a.s the proper timing of the valves is as definitely related to the position of the piston as is that of the spark, and it is possible, so it is said, to complete the job of valve timing in two or three minutes. As it. is necessary,, when decarbonizing an engine by burning out, that. the piston must, to ensure safety', be on tap dead centre, with both valves closed, the tester enables the correct position for this work to be quickly obtained, so that its use should effect a considerable saving of time in the engine testing shop.