is it possible for an engine knock to come and go? whenever i have heard one its usually constant but i just want to rule out the possibility?

also what would cause a knocking to come and go?

If the knock is most prevalent when cold or upon startup, it could be piston slap. This is pretty well documented with some Chevy engines. It's more annoying than harmful.

no knock on startup. but from what i have seen being its not constant it elimantes a rod knock

if its at Idle warm probrably mains, I had a new motor knock off and on for 6mos once and it eventually went away? Dont know why or what it was and didnt know enough about motors to figure it out.

well going from what he says its completely random, engine might have been running 2 hours then a knock or could be 3 minutes after startup and then it goes away.

he was told pwer steering pulley/pump but i have never heard one knock.

what's your oil pressure like? how old is the engine? i had the same problem but it was caused by my oil pump going south on me (down to 20 psi at idle)#1 top rod bearing(one closest to the piston) was down to the copper. it would knock at a warm idle but not at speed.so b4 it got any wrost i drop the pan and took a look. and that's what i found. the engine wasn't even a year old.I took the pump back to the parts store and they gave me and other one(no charge) but after reading about the 55hv. i decided to go with another pump.this was my problem it mite not be the same for u.just thought i pass on what happen to me.

loose converter bolts, loose balancer, bad water pump all can give off knocking noises

loose converter bolts, loose balancer, bad water pump all can give off knocking noises

Agreed.