Several things can cause a knock.
low octane gas
worn bearings
timing not set correctly
or even something loose on the outside of the motor
bums
It can mean that the engine has a bad main bearing. Can also mean one of the pistons are bad.
No
warped rotors
When your engine has a knocking noise, it could mean that a rod has been thrown. It could also mean you are low on oil.
I Hear You Knocking was created in 1970-11.
When an engine is cold, the oil is thicker, and flows slower. When oil doesn't get to valvetrain components quickly, you'll hear knocking, also known as valvetrain clatter. As the engine warms up the knocking should go away.
Can't You Hear Me Knocking was created on 1971-04-23.
You'll most likely hear a knocking sound or squeaking of some kind
rebuild the motor or buy a crank kit and install it.
knocking noise
you may have trown a rod.