The Real Number
nitially all engines have a manufacturer-specified static spark timing. Combustion, and therefore, cylinder pressure build-up is a rather slow process. In order to have the cylinder pressure peak at the proper time in the power stroke, combustion must be started before the piston reaches top dead center (TDC) on the compression stroke. The higher the engine rpm, the earlier the required spark. The spark coming in advance of TDC is measured in degrees of crankshaft rotation. Some engines like John Deere, Economy, Sandwich, R&V and others have the spark time mark stamped or cast on
