I want to hang on to my old rig and am exploring options for making it work. Your thoughts are appreciated.

It has low (but not tragic) compression, burns crazy oil, a cold start knock/rattle (that is not caused by bad timing tensioners, as I replaced all three), a knock at and above 4k rpm, and internal wear as indicated by oil analysis. Recently I have discovered low oil pressure to add to the list. By low I mean 5 psi at idle and ~35 psi at 2k rpm (Spec is >14 at idle and 40 at 2k).

Despite all this, it runs pretty well. For now.

I am trying to figure out whether it is worth it to replace the oil pump before replacing the engine. I'm specifically wondering whether it might help with the low oil pressure and knocking. If so, I would then do another oil analysis to see whether the low oil pressure was the cause of the accelerated wear. I'd be doing the work myself, so labor cost is not an issue.

Although replacing the oil pump is no picnic on this car, it would be a lot cheaper than replacing the engine. However, I'd be kicking myself if it didn't help at all, which is why I am here asking for advice. My alternative is to roll the dice with a good used engine or perhaps have it rebuilt, depending on how much time and money that would cost.

What do you think?

Felt bad seeing this post for more than two weeks now without a reply so here's my two cents, for what it's worth. Obviously, as you have described it, your engine is hurting in ways that only a replacement or total rebuild could resolve. That would be a great deal more work than just replacing the oil pump and cost a great deal more as well, as I know you are well aware. Without a doubt, low oil pressure will cause accelerated wear and it's just a matter of time before the engine gives up the ghost if you don't do something. If it was mine and I had the down time available but not the funds for a replacement engine, I would go ahead and replace the oil pump. It would probably help add some longevity to what's left of the engine's life but that depends on how far gone are some of the other parts that are worn and/or wearing out. Best of luck to you.

That oil pressure isn't great, but it's doable. You might want to put a little thicker oil in there, or at least run synthetic which can have stronger film strength, but really it's not awful. It is low, but you do have pressure and presumably flow, which is the even more important part. My MO is to fix things, not replace them, but with the amount of work to just replace the pump, let alone rebuild it, I'd treat it in a more hospice manner almost. Keep it full of oil, a little thicker, which given your location might be a problem still this time of year and don't overstress it too much.

Thanks for the responses.

I am starting to look around for a replacement. I think the wear is pronounced enough that doesn't warrant replacing just the pump.

With the wife home with the kids due to shelter in place, it would be a good time to replace it, actually.

Until then I am keeping it full of oil and taking it easy.