if a head gasket is bad could it cause engine knock and low oil pressure.

 

A engine with a failing head gasket may "knock" Specificly detonate, or sound like a bottom end knock if the motor is overheating. Won't generally cause low oil pressure.

 

well thats probly what happend i overheated it started it back up and had a slight knock i know its not a rod or bearing and has some white smoke coming out of exuast. if everything goes right how long would it take to change headgaskets if everything goes smothley. thanks

 

All day. In the driveway.

 

If you lost the head gasket you most likely warped or cracked the head or heads as well. Check them very carefully when you remove them. While they are off you might as well send them out for a valve job.

 

well we pulled the heads off yesterday nothing wrong so it has to be in the bottom end. took about 3 hours to get everything unhooked and ready to pull probly tommaro i thought it would take alot longer than that. all the valvetrain look ok so cant wait ot find out what happend.