An internal combustion engine is so constructed that {HEAD ~ the timing} of {TAIL ~ the intake and exhaust valves} can be changed during operation of the engine making it possible to select the optimum timing for the valves in accordance with the operating conditions 
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An internal combustion engine is so constructed that { HEAD ~ the timing } of { TAIL ~ the intake and exhaust valves } can be changed during operation of the engine making it possible to select the optimum timing for the valves in accordance with the operating conditions
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH