To convert ci to L divide by 61...
with units, it's actually 61 ci/L...
so (396 ci) / (61 ci/L) = 6.49 L
so then the fraction increase = 6.49 / 5.7 = 1.14 (rounding to 2 places)... so about 14% increase in displacement.
Joecar explained that perfectly!!! For my combo I figured the % difference in displacement from 325ci to 408ci. Then I multiplied the table by the percent difference. I still have to fine tune everything anyway but the engine fired and ran on the '01 Silverado tune with all the fueling modifications but I couldn't get her to fire with the '01 f body tune for some reason. And of course I need to use the f body tune because it's a factory 6 speed tune. Lol!
No worries.
The basics are: airmass, fuel (which is proportional to airmass), injector data, spark advance, idle.
The GM PCM's are a bit more difficult because they have built-in sanity checks and saves (e.g. fueling is determined by richest of the currently active tables, and negative trims are never applied to PE/WOT).