rattle

[79gmcc15]

hey guys, got another question. sometimes I hear a rattleing comeing from my moter. it happens randomly, I could be driveing along or siting at a light and it would happen or drive all day without it happening. it reminds me of a sanke rattle. its not a taping noise like you would get from a lose rocker. I suspect a rounded cam lobe, and the reson is, is becuse I stupidly and unknowingly over tightend the rockers on the passenger side and drove it like that for a while. because I had a lose rocker *long story*. and when I got them adjusted proberly by a pro he noticed that the #4 cylnder I beleave "Intake" side was hard to turn. mabe bent a bent rod of some kind or valve stem? and the truck does sometimes reverse backfire under load*ie going up hill mostly*. dont know if that means anything pertaining to the problem and it does have a miss in it and its not from fouled plugs cause I put new ones in and check them offen cause the #3 fouls offen with oil so I try to keep up on them and clean them of. I also have a 430-50 cfm carb *came with truck* dont know if that has anything to do with anything but trying to give you as much info as I can, and it is a 350/350. and just rembered I do seem to have low oil psi, at idle its between the 2nd *15psi?* and middle *30?* and sometimes stays that way or below that when driveing, and something that scares me is that on the interstate after driveing it a 3-5 miles, sometimes its barely above the first mark and most of the time the oil is full..... and yes I know I need a new moter. but theres no way I can do that right now. thank you.. matt