Is there a procedure for changing timing chains on a Datsun U20 engine that does not require engine removal?

Yes, it is possible to change the timing chains on a Datsun U20 engine without removing the engine from the vehicle. The procedure typically involves removing the front timing cover, which may require removing other components such as the water pump and oil pan. Careful alignment of the timing marks is crucial during reassembly to ensure proper engine timing. Always consult a repair manual for detailed steps specific to your engine model.