What would cause a loud knocking sound and scratching sound in the 3.1L chev Lumina motor?
Not sure what your asking exactly. But I will tell you this about knocking in Montanas. I have seen a few of them that will start sucking oil into the combustion chamber through a leaking intake manifold gasket. The motor goes dry enough to cause a knocking on the lower end of the engine. End of motor! Check your oil!!!