ENGINE KNOCK 81 GMC 1500 (350)

I would expect the engine is damaged.
You'll need to check the oil pressure and try to narrow down the area where the sound is coming from to proceed.
A very loud knock is probably a piston or rod bearing.

Sounds like a tapping maybe lifter. Maybe valve check under valve cover.

i have the same problem. KNOCKING. Appears alot of others are having this problem. Sounds like some kind of recall needs to be done!

Not sure but you may be having problems with your oil pump

have it tested using a manual gage if still low then main baring ore most likely bad that would mean a over hall if is really low and bearings bad should be making rattle noise when started up first few seconds

Most likely cause is a hydralic tappet. Mits are well know for top end noise. Note we are talking about a tapping or clicking sound not a knock. You can try using an engine flush product if the noise is getting bad and then changing your oil. Generally if the oil is not changed regularily eventually the tapping noise gets happens.

a knock sensor is basically a resistor and a spring, and what it does is it reduces valve ping. Valve ping is when the fuel is not properly burned and tries to explode before the valve is fully closed and it will make a pinging noise when under load or at higher RPM. If the sensor is bad it can cause detonation, detonation is when the fuel explodes before the valve is closed and can cause a cracked, or exploded piston, bent valves etc. Your problem does not sound like that of a bad knock sensor, predominantly you will only hear the "ping" under load and not at idle and if it was bad your check engine light should be on. this sounds more like a rod knock. change the oil again and use only AMSOIL and an amsoil filter, amsoil is proven to last longer than any other oil, 600,000 miles without a change, or a filter change.

can be a big fix. youmay want to try a motor flush (engine oil)

Engine knock Huh? In order to qualify the term "Knock", Let me get you to perform some simple task/observation. Typically, if you hear a noise on top of your motor that can be described as a light knock, usually going tap, tap, tap, tapping along at double the tempo, of your motor spinning, Your oil pump may be having trouble getting oil to the top where the valve's and rocker arms are. If you hear a "Knock" by bending over or kneeling beside one of your "front wheel well's"and stick your head up to the well, providing a vantage point to "hear" whats going on at the lower part of the engine. A knock from here will/can indicate a potentially overheated, under lubricated, rod or crank bearing that could seize the motor. This (theretical) crank bearing would be sounding off at half the tempo of the rocker arms above., with a deep, dark klunk that would defintly present itself as the sort of noise that damages metal parts. Now, that being said.....common sense goes a long way, people....1.) Most people are aware of the maintenance that has been performed on a particular engine, the quality and quantity of that maint. and when the last time it was ran out of oil or water. For those who fall into the " lack of maintenence" catagory, you probably already know why your engine or driveline sound as it does. If you happen to take particulary good care of your car, there is a good chance that whatever noise or "happening" might be going on, it'll be much easier to remedy. There are always exceptions to every rule. Remember, its not what will happen, it's what can happen. Take care of your car, and it will take care of you. Theroad

could be rod with that amount of miles