Not an expert on this but if you line BORE (not hone) the mains on your block because you have missmatched main caps or new main caps, the boring changes where the center line of the crank rides in relation to your deck height. Therefore the distance between the center line of you crank is closer to the center line of you cam, therefore a standard length timing chain will be loose.

That's muy understanding

Frank

Remember - 2 wrongs don't make a right - but 3 rights make a left!