Methods and systems consistent with the present invention overcome the shortcomings of existing trading systems by providing an invoiceless trading system that creates incentives for customers to pay suppliers within a predetermined period of time, such as a settlement period. The controller controls the relative rotation phase of the exhaust camshaft in accordance with the relative rotation phase of the intake camshaft. The positioning members comprise attachment devices suitable to connect at least a first plate to a wall of the support frame, and thrust devices configured to compress the other plates with respect to each other, in correspondence with respective connection edges and against the at least one first plate. A screw extends through the barrel and engages the saddle.