Patent ID: 8881391

Claim:
A method for producing a hollow engine valve in which a hollow stem portion of a semi-finished product is shaped into a predetermined shape by sequentially inserting the hollow stem portion into a plurality of shaping holes different in hole shape to sequentially draw the hollow stem portion in such a way that an outer diameter dimension and an inner diameter dimension of the hollow stem portion are reduced stepwise and a length of the hollow stem portion is increased stepwise, the method for producing a hollow engine valve comprising: subjecting the semi-finished product to heat treatment in such a way that a hardness of the semi-finished product becomes equal to or less than a predetermined hardness; and making a wall thickness of a portion between the hollow stem portion and a valve umbrella portion connected to a lower end of the hollow stem portion larger than the wall thickness of the hollow stem portion and a wall thickness of an upper portion of the valve umbrella portion shaped by the shaping holes.