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Let's for just a brief moment, get technical.....
5.3 liter = 323.425 843 702 cubic inch, however....
323 cubic inch = 5.293 021 672 liter
So, is 5.3 rounded up, or rounded down.
327 cubic inch = 5.358 569 928 liter
Could GM have just rounds 5.385xxxx to 5.3 ? But they could have called it then a 5.4 (no...too close to Ford).
But it could be a 325...
325 cubic inch = 5.325 795 8 liter (rounded off nicely would be 5.3l).
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Who cares! I'm from a metric county. 5.3l works. 
