I thought the rule of thumb on n NA motor is was .001" X bore for the top ring and .0025" for the bottom ring?

And for a boost motor it was .0055" x bore for the top ring and .0065" x bore for the bottom?

My father inlaw gave me these number and its how he's been building motors since the 60's. I know times are different and he hasnt built a motor in the last 10 yrs or so but he's built 327 motors making 475hp NA, 455 Pontiac motors making 600hp,.. so I hold his 'old school' skills with a very high regard.

But are those numbers correct for todays motor builds or have things changed?

Hurst