Cylinder bore specs for an engine rebuild
 

Hi forum. I embarked on the improbable quest of rebuilding an ACL engine (improbable because I have never done anything like this).

The specific question of the day has to do with cylinder bore measurement. I have to measure them with a dial gauge to decide whether they need to be rebored or not.

I got two manuals, one from Volvo and one from VW, and they give different tolerance levels. Both say I should measure perpendicularly and longitudinally at three different levels of depth.

Volvo says a rebore is necessary if "any two points are more than 0.04mm from each other", while VW states "if any one point is > 0.1mm away from original spec".

I measured nothing more than 0.1mm from spec, but I do have cases of 0.06mm difference between two points in the same cylinder.

Which one is right? Or is a rebore a good idea anyway given the engine has already 270k km on the clock?

Sorry I don't have the answer, but I would be temped to compare to a third source. Can you find a Bentley manual?

Compression is a better indicator of cylinder wear. If all cylinders are below 35 bar it's probably time for the overhaul.