Knocking noise

Could be piston slap, a rod knock or a worn wrist pin.

Cold or hot? If only cold: piston slap; if when hot rod knock. This one's old enough that replacing motor is out of the cards. Just keep coolant and oil up to snuff and don't over rev under load...you could get lucky and drive on this weak plateau for a long time. But if the knock gets progressively worse expect for the motor to crap out while running, at which time chasing a used motor would not be cost-effective given age. Good luck. Note that running synth oil won't help...neither will additives.

To be clear: piston slap self-corrects as motor warms and the pistons' travel becomes perfectly horizontal, so just don't over rev when cold; but usually it's only audible on acceleration...not decel. So I suspect you've rod knock at temp. You can verify also by warming motor and with quiet ambience just revving motor off idle, listening carefully for the knock.