I bought a 1997 GMC ext. cab short bed 1500 with about 167,000 miles on a 5.7 L31 Vortec engine. I have built older GM engines before, but I have never touched an L31, or any Vortec engine for that matter. Long story short, it has what I believe to be lifter knock. What happens is the engine always ticks on start up until the oil pressure comes up and sometimes a little bit afterward. It intermittently ticks while running; sometimes it wont stop ticking after start up and sometimes it does. That is why I am thinking it has a collapsing lifter that doesn't always collapse. So I was going to replace the lifters. From what I understand, since this engine has a roller cam, I can replace just the lifters as long as the cam is in good shape. Is this factual info? Any other things anyone can tell me about this engine before I dive into it? I know very little about this engine other than it still uses the old 350 style block, but with Vortec heads.
Also, it is throwing a P0430 Catalyst System Efficiency Below Threshold (Bank 2) code, so I guess I am going to go see how much it is to get new cats installed on it.
