I have a 1986.5 Toyota Supra 5 Speed N/A 7MGE. So my car was driving very well, but then at around 3k RPM's I heard a knocking sound that was pretty quiet. As I drove more the knocking got louder and I could here it at lower RPM's. Now even when it's idling I can hear it and its pretty loud. Also when I'm driving in third gear and then press in the clutch pedal to shift it makes a grinding sound, but only in 3rd gear or higher. When it first started making the noise I took it to my mechanic and he told me to start it and rev it, right when he heard it he told me it was something bottom end of the engine like a bearing, rod, etc. But I just wanted to see if it could be something else and get peoples opinions on what I should do. Thank you