ka24e noises

[casey115764]

Ok so I bought a 1990 240 hatch with the stock single cam ka in it. After i towed it home i put a new battery in it and it fired right up and sounded pretty nice. I didn't want to drive it with the old oil in it so i did an oil and oil filter change. I don't know why nut i put 5w 30 in it and started it up and the lifters were ticking so after driving it for about 15 miles i drained the oil and put some 15w 40 in it and it didn't quiet it up so I took the valve cover off and checked the lifters the 2 intake rockers/lifters on the 2nd cylinder were soft so I went up to the local wrecking yard and bought a whole intake rocker arm assembly. After I installed it and started it up it was pretty much fixed just a little noise left. So I started driving it and i noticed there is a different noise that happens when you hold the car at a steady rpm. It will do it at any steady RPMs over 1500. Then the lifter noise came back again so i took it back apart and 2 different ones were soft so i replaced those with some extras and again it quieted up. then about 5 min of driving it came back again so I took it back apart and two more were soft one that was soft was one I already replaced. I think that the steady rpm sound is the timing chain hitting But i have no clue why the other lifters keep going bad. Could it be because of low oil pressure, my cam or what. If you made it to the end of this over sized question and you know what it could possibly be then your response would be greatly appreciated.