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Hi everyone. It’s my first time here but I need some help. My 2007 Silverado with an LH6 5.3 DOD motor has intermittent oil pressure issues. Alittle back story, the truck has 274k on the original motor. Recently, I replace the valley plate gasket, but only the outer part. For convenience sake, I left the DOD tower gasket part. After that, I replaced the oil pickup tube o ring and gave the truck a full service. My issue now is, I still have intermittent low oil pressure. I’ve read about a service bulletin where the oil pressure relief valve sticks, which requires replacing the oil pump and such but there are so many possibilities I’m not sure what to pursue. I know the oil pressure sensor is good and the screen below it is clean. The issue happens randomly. I can start the truck and it will idle and warm up fine (maybe slightly lower than usual) and then I can drive it. I’ll be sitting at a light or a stop and I can slowly watch the oil pressure fall off. Sometimes even while driving slow and then the oil pressure stays low or 0. It doesn’t cause any bad noises that I know of because I shut it off immediately but I’m so confused. After letting it sit for a bit and starting it up it’s fine. I’ve heard many possibility between it being the oil relief in the pump, the oil relief in the pan that apparently exists, DOD lifter problems (although they aren’t giving me any bad noise) leaking DOD valley gaskets (the ones I skimped on replacing) and more. I’m lost as to what to do. Can anyone offer some insight? -
A few months ago I bought a 2007 GMC Sierra (new body) with 150,000 miles on the clock. It has the LH6 in it. It has since gotten cold outside and when I start it in the mornings It has what I am sure is a rod knock. It goes away after the engine warms up. It has good oil pressure. I have always been a ford guy and wasn't too familiar with these engines otherwise I would have avoided these early AFM engines like the plague. It sounds a lot "deeper" than a lifter click. I have removed the valve covers and confirmed that I don't have a collapsed lifter or flattened cam. The thing consumed over a quart of oil in the last 2,000 miles. I had a cylinder 1 misfire and when I pulled the plug it was pitted and the porcelain was cracked showing tons of detonation. I replaced the plug and that fixed the misfire. All the other plugs look great. Onto my question. With all these issues an the reputation of these AFM lifters and oil consumption I kinda want to get ahead of it and plan on putting an engine in it. This is my daily driver so i need to minimize down time. I was looking to get a block and get it ready to go in the truck (as money permits) so there is no huge rush or surprises. The problem is these specific LH6 Aluminum blocks were only used from 2005-2009 and are not the easiest/cheapest to find. The LY5 however is the iron counterpart to it and cheap and easy to find since they produced them 2007-2014 and were more common. I don't care about the 100lbs. Does everything bolt up? And would the computer freak out? I plan on eliminating the AFM and putting some trustworthy lifters and a cam in it so I will need some computer work done anyways hopefully it can be programmed enough to handle a different block? Would someone with HP Tuners be able to do the computer work or does the whole thing need to be sent off/replaced?. I've rebuilt a few engines It's just this computer stuff that gets kinda hayzey. If I am deleting the AMF is there another Gen IV block that would work for this application? Screw it and get a 6.0 and stroke it?
