Assessment of engine condition ...

[cub builder]

The IO-540 has an adjustable oil pressure relief valve. A normal oil pressure of 60 psi only indicates to me that you might want to adjust the oil pressure relief setting up a bit by adding a couple of washers behind the relief spring. The compressions do seem a bit off, but that doesn't really tell you the story. While doing a compression test, where is it leaking? Rings or Exhaust valves? So the engine might need to be topped eventually. But I would want a really solid logbook history of the engine, in particular, a parts list from the last overhaul indicating what all was oversize or undersize and by what amounts, as well as whether these are overhauled cylinders or new installs at the last overhaul. I would guess they were probably service limit cylinders that were honed with new ex valves and guides, which is probably why the compressions are off a bit and it's using some oil 700 hrs later. For cylinders, I've used a lot of refurb service limit cylinders over the years, but there's nothing like new if you want low oil consumption and good compressions. I don't go with refurb cylinders anymore if I'm going to do a complete top or a major overhaul. They either meet new spec, or I'll buy new. Makes for a much happier engine and owner in the long run.

IO-540 oil pressure.pdf

In the attached.pdf, you'll see the drawing of the oil pressure relief valve. Note in the parts it calls for a maximum of 9 washers behind the spring. Typically, 3 washers is about right. The relief valve is easily removed without doing anything else to the engine. Item #6 is an optional adjustable oil pressure relief. The engine could be equipped either way.

-Cub Builder