My take on the oiling system crossover tube for the small block

Retroboy said

Engine shop I worked in years ago fitted undersized cam bearings to every engine regardless of what it was and the engine assembly guy reemed them to suit.

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FWIW..... That was standard assembly procedure for Opels, and probably Holdens, in that year range.... 60's-80's and maybe earlier in time. You could not buy cam bearings finished-to-proper ID from the factories for the Opel CIH engines of that era. So it had nothing to do with clearances or alignment in some cases... it was just what had to be done for standard replacement procedures.

Fiat's were the same way in that era for simple bearings like the oil pump shaft... really sucked if you did not have the tools. Since I did not have the tools, I let my Opel cam bearings wear to some pretty big clearances LOL