Melling pump cover bolt torque

New pump? Then something is wrong in the pump or how it was machined (housing not machined deep enough, or either rotor too machined too tall). Pull the rotors out and see if something is underneath, or if there is something sticking out the bottom of the cover or on the top or bottom of either rotor, or either rotor is not seating fully. With the pump bolted in place, there is a small clearance of a few thousandths between the cover and both rotors.