I replaced the timing belt and the water pump, and now I can hear a knocking sound. I suspect that the timing is off.
In the interest of your safety, I would avoid driving your car. According to Chevrolet, the motor in that particular car is an interference engine. This means that, if the timing is off, the valves can make contact with the piston, and bend valves, and break pistons. The damage has probably already been done if you are hearing a knocking sound.
I would start by lining up the timing marks to determine whether the timing is, in fact, off. A mechanic from YourMechanic can inspect the source of the noise, and inspect the timing, to determine whether it is off. If this is the case, you will likely need to have the head rebuilt, at a minimum.
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