A couple weeks ago I heard a loud tick, so I pulled my top-end apart. I found a blown head gasket with coolant in my oil and everywhere else. Also, my lifter on the #1 exhaust was broken (middle was pushed down), and the sides of it were dry. The rest of the litters looked fine, but I bought all new anyways. I soaked them in oil and put them in, and got all new gaskets for the top end, put the motor back together. It ran and sounded good for about 20 minutes, and the tick is back. Is that lifter not getting any oil and the sound I hear is the metal sides of the lifer rubbing on the metal sides of the lifter slot? Or is it something else? Any help would be appreciated! By the way: it's a 2001 Silverado with 118,000 miles 5.3L 4x4.