I recently replaced the B-18 in my 65 122 with a 73 B-20. The new engine runs good and has good power but uses a quart of oil every 500 miles. It doesn't smoke and there aren't any big oil leaks as both the front and rear main seals have been replaced. A Volvo guy I know says the problem probably is that the exhaust system is too small. He says there is too much back pressure and the oil is blown out. When I changed the motor I just used a reducer to connect the exhaust manifold to the old system so it is a 2.25 inch pipe going into a 1.5 inch pipe. Do you think he is right? I would appreciate any input.