N62394Boeing A75N1(PT17)

The pilot reported that the airplane had a lower-than-expected climb rate during initial climb which was followed by a rough running engine at all power settings. The pilot entered a turn to remain close to the airport during which the radial engine quit momentarily before it resumed running rough. The pilot declared an emergency with the tower controller and was cleared to land on the runway, which resulted in a tailwind condition. The pilot was unable to maintain directional control during the landing roll which resulted in a ground loop and a runway excursion. The airplane sustained substantial damage to both ailerons and the aft spar of both lower wings.