US Patent 7100744 Internal combustion engine

An engine is described having a hole for a dipstick which is closed by a cap from which the dipstick depends. The engine body is formed with an overhanging lip adjacent the mouth of the hole, and the cap comprises a spigot rotatably received in the mouth of the hole and a flange extending radially outwards from the spigot to cover the mouth of the hole. The flange is non-circular so that by rotation of the cap relative to the hole, a radially projecting portion of the edge of the flange may be selectively engaged beneath the overhanging lip to prevent axial displacement of the cap and the dipstick relative to the engine body.