The engine came out of a 70's suburban. Its a 454. I had some valve chatter that seemed to get louder each time I drove the car. I thought a lifter was clogged so I changed the oil thinking some fresh sythetic might clear it. The chatter got much better as I drove the car. Suddenly the engine quit for a second then ran fine. A mile later it got very rough with extreme missing. I had to put it in 3rd to keep up speed. When I got home I checked the coil specs and it's ok. I could still hear ticking under the drivers side valve cover. The next day I let the engine warm up and put my hand over drivers side exhaust and it was extremely rough and cold while the passenger side was even and warm.
Any ideas what my problem is.