Well, not to say that your problem is the same as mine, but when I ended up with 6 bent push rods I did get the tick tick tick sound. replace the push rods and two lifters and ran it for about a month and a half when I hung a valve open and destroyed the engine. Should have redone the heads when I did the pushrods but I wanted to test some other stuff first and you know one thing leads to another and then one day BANG and no more cylinder, piston, rod or cam. Might want to think about having the heads done if your motor is "old" like you say.