TheFlyfish

I have taken the heads off a 4.5 16V engine and measured the cylinder bores. The diameter difference from the top of the bore(where the rings don't run) to different points deeper down the bores, are just below 0.02 mm(0,000787 inch)

(Measured with a 3 point gauge, with an accuracy of 0,005 mm(0,000197 inch))

I don't know how many miles or km this engine has been run, I bought it as a loose unit, for my boat engine project.

I have not been able to find a wear limit, but how does this sound to the people here?

WallyP

Cylinder wall wear is very, very rarely a problem on the 928 engine, barring lubrication failure, glass bead contamination, etc.

The wear you are measuring (much less than any normal device could measure ) should not ever be a problem.

GregBBRD

You've measured wear in the low wear area down in the bore and compared that to virgin area above the rings.

Which has given you a baseline of the original bore size.

Now measure where the rings wear the most (at the top) and measure how "round" the bores are in various places.

That is the information you need.....