So in the hunt for a replacement engine for my AP1 I'm seeing there are two main types:

Used engines from dismantlers, importers, salvage yards. Typically have a warranty that excludes accessories, and sometimes excludes the oil pump.

Private party used engines, typically as-is.


If you had an engine with a warranty, what would you check?

I think at bare minimum it makes sense to inspect and replace the intake valve retainers and do a valve adjustment. Is it worth pulling the oil pan to check the pump?


With an as-is engine, is it worth pulling the head to check the bores, even with the added cost of a new head gasket? Is it worth preemptively replacing the bearings and rings in the bottom end? What other maintenance is worth doing?

 

I would pull the valve cover, inspect the retainers (replace if needed), replace the plugs, and adjust the valves. I may consider dropping the pan and looking for metal, but I personally would go no further than that. I certainly would not do rings, I don't think you can just replace the rings without then doing some type of honing, but maybe I am wrong.

I would follow up with a compression test and UOA to get a baseline and then follow up on both the first couple oil changes to see how things are going.

 

Bare minimum would be a leak-down and compression test.

If you're going to buy used and replace parts (rings, bearing, etc.) why not just rebuild what you have now?

 

Reasons not rebuilding what I have now:

1: cylinder walls in #1 scored, not sure if is under .25mm depth
2: unsure if I can find a machine shop to handle it if not too deep
3: if I hone the cylinders .25mm over, I need new pistons ($$$)

I'd totally be willing to buy just a short block as my head is totally rebuildable, but they seem to be scarce out there.

Rings do seem like overkill if the leakdown/compression looks good. Rod bearings are easy enough, but like you said, it might be overkill.