FIELD: mechanical engineering. SUBSTANCE: in gas engine recess in piston for combustion chamber is form by conjugated spherical surface and surface of truncated cone and/or cylinder pointed with its base to intake channel which is made profiled to create directed motion of gas-air mixture around cylinder axis. Diameter of base exceeds diameter of sphere, and spherical surface in form of semisphere can smoothly blend into surface of truncated cone and/or cylinder. Spark plug can be installed in spark plug channel at tilting relative to cylinder axis to form conical space in channel under spark plug. Vertex of cone is arranged in zone of lower part of spark plug, and base is arranged in plane of gas joint of cylinder head completely above recess in piston. EFFECT: improved performance of converted engine at reduced labour input for converting. 2 cl, 9 dwg
