Combustion chamber construction for engine

A combustion chamber construction includes inlet and exhaust side sloping surfaces. The inlet side sloping surface is formed on one side of a pentroof apex portion as a boundary and which has an inlet port. The exhaust side sloping surface is formed on the other side of the pentroof apex portion as the boundary and which has an exhaust port. A flow improving portion is formed between the inlet port and exhaust port. The flow improving portion includes an inlet flow surface which is formed by recessing part of the inlet side sloping surface and an exhaust side guide surface. One end of the exhaust side guide surface is connected to an exhaust surface of the exhaust side sloping surface and the other end is connected to the inlet flow surface. An angle formed by the inlet flow surface and the exhaust side guide surface is smaller than or equal to an angle formed by the exhaust surface and the exhaust side guide surface.