My car sounds like there is a loud knocking noise comin from the engine

knocking or clanging usually means engine rebuild or replacement
What is piston rod knock Engine Knocking Yahoo Video Search Results 3 Causes of Engine Knock

timing could be off or try higher octane gas

any smoke could be a fuel knock if u have a injector leaking off.

it means that you need to research either a different car, or a different engine for this car. A loud knocking noise indicates a connecting rod is loose, and your engine has little to no time left before the rod or endcap breaks, completely messing up your engine, and making it very difficult to change. If you must drive it, drive it slow, and be super gentle with the gas...like you're driving on ice. If it's more of a ticking noise, that could be a lifter, but a loud hollow sounding knock is a rod. You may also have a check engine light showing up on the dash from the knock sensor.

Have your air compressor for your air tested. Sounds like its bad.

Here's what you don't want to hear...A loud knocking noise from inside your engine is generally caused by a crank or rod bearing...when caught very early, sometimes they can be replaced. however, once the noise is loud, the attending crankshaft journal gets "hammered" out of shape and the job becomes very expensive and in most cases more costly than engine replacement. There is one other item that can cause a loud knock...your flywheel. Bearing problems generally cause low oil pressure. If you have that, it's gone...if not, have the flywheel checked before sending the engine to the scrapyard.

It sound like you dropped valve seat on the head. Did you recently over heat your engine .

you have a rod going out on the car

how is the oil level and pressure?, how many miles on engine? is this a loud knock or rather a clatter/ticking noise? knock is engine rod or crankshaft bearings, clatter loud ticking is valve follower noise. how long before it (the noise) goes away?

what kind of sounds is it making a knocking sound or a exhaust sound might need a tune up