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This is an updated version of the tachometer drive used on FF2000 engines. The new billet construction will provide many years of reliable service. Bolts directly in place of the original and accepts the same Smiths-style drive cable on the output.
This gearbox provides 2:1 speed reduction. Because it will be driven by the camshaft or oil pump, the input is already turning at 1/2 crankshaft speed. The cable will then be driven at 1/4 crankshaft speed, which will require a 4:1 ratio mechanical tachometer. The "black dot" indicates a non-reversing drive: A clockwise input (as on FF2000 / S2 engines) will turn the output clockwise. (Smiths tachometers are direction-sensitive; Jones tachs are not.
Note: This gearbox is designed to take the thrust from the scroll gear in one direction only. It is designed to be driven by a clockwise input. Applications with a counter-clockwise input direction should use our Brown Dot (Reversing) Tach Drive Gearbox (Part No. 166-20).