The disclosure embraces a charge forming apparatus or carburetor and method of operation thereof wherein the charge forming apparatus is of modular construction and is inclusive of a body construction and a fluid flow control construction associated with the body construction, the fluid flow control construction being of laminar character fashioned with open areas or passages accommodating fluid flow or transfer, the fluid flow control being of a character enabling the interchangeability of fluid flow control laminations having different or modified patterns or arrangements of open areas or passages whereby the method of operation or the operating or metering characteristics of the charge forming apparatus may be changed or modified without alteration of the body construction. The provision of interchangeable fluid flow control laminations or members facilitates standardization of the body whereby the standardized charge forming apparatus may be rendered usable with engines of different sizes and operating characteristics by employing a fluid flow control construction having a selected orientation of open areas or passages accommodating fluid flow.