every time i start up my car i hear a knocking sound, also when i run the car on the freeway for a while, when i get off i still hear the knocking, once i guy told me it was the oil pump, is he right? i need help on knowing whats the problem. i got a 79 gmc 231 v6.

Could be the oil pump. It could also be Rod Knock (spun bearing) which could also be caused by the oil pump going bad and not providing enough oil to the motor. I would say no way to really tell until you open the motor up.

thx, i'll try changing the oil pump and see what happens

With the engine warmed up, have somebody hold the throttle at about 2500 rpm while you listen under the car. Be careful and maybe use a stethoscope, but if you listen to the pan and hear the rat-tat-tat noise, it most likely is a bearing.

I have had a bunch of these turn out to be loose flex plate bolts.

where are these flex plate bolts

(i need help on knowing whats the problem)

To be honest I can't beleive anyone can ask us for a "direct" answer to whats wrong with their motor over a forum. We can only give a "guess" on what "may" be wrong. :? We are here to help or guess, but if you want a real answer, take it to a shop or have someone look at it where they can see and hear it running. :)

where are these flex plate bolts

They attach the torque converter to the flexplate. (Between engine and trans.)

oh u mean the flywheel, ya i gotta check that, someone told me to check it too.

oh u mean the flywheel, ya i gotta check that, someone told me to check it too.

If it's a standard trans it's a flywheel, if it's and automatic it's a flexplate.