My '98 Suburban 7.4l with 105k miles has developed a ticking noise on the top side of the engine - sounds like it could be a rocker arm, but I'm guessing the real culprit is a failed hydraulic roller lifter. I drove the truck about 100 miles on Sunday with no problems. It sat in my driveway for a few hours until I was going to park it in the garage. I heard the noise and it didn't go away even after warming up the engine and driving it around for about 10 miles. Thoughts? I'd like to hear anyone's experience with this before I start taking the top & front of the engine apart in order to change the cam & lifters, timing chain & gears, water pump, & anything else that may need replacement in this unexpected project.