My car runs fine still but about 3 weeks after i bought it i noticed a knock in the ngine as soon as u started it up. It will go away after about 4 minutes of running but embarrasing when cold starting. Problem does not occur if engine is warm and if my car is parked facing downhill in my driveway. What could it be

Wild guess...

Might be piston slap (worn bore and piston). Might not make the noise when the car is pointed downhill because the oil in the pan might be partially covering the crank. When you start it up, the crank would throw oil everywhere and help lubricate the cylinder walls.

Again, this is just a guess.

it'd help if you said what kind of engine and what's in it or been done to it. WAG but i'd think piston slap also.

guess but what is the oil press on start up is it mabey not getting around the engine quick enough at startup or the oilk too thin?? seems like opposite to normal when the engine knocks once its warmed up? is it a knock salp ping hollow what

this is a long shot but it worked for me. i used to hear a knock when it was cold or at certain positions. turned out it was my alternator, and becuase my engine shook more when it was cold, it made a knocking noise from something that broke loose inside of it. i thought i had a rod knocking for ever but it turned out to be the damn alternator. worth a try but its a VERY long shot.

Maybe you could have someone listen when you first start up the engine? They might be able to isolate where the sound is coming from. A mechanics stethoscope would be very handy about now!

ok sorry that i didnt mention it its a 305 tbi. I've tried thicker oil hoping it would stay up in the engine better. Worked a little but still not great it sounds like a knocking. My dad is a mechanic and he says hes not sure but hes all about if it runs fine then whats the big deal. But it is kinda loud especially coming out of school after having it sit there all day and starting it up.