Why are Engine Sizes in Liters instead of in cubic inches ?

[Ragamuffin]

Can someone explain why the U.S. automakers making vehicles in the U.S. market changed to labeling engine sizes in liters instead of the olden days in cubic inches ? Also, as stated in a previous thread, I am not very mechanically/engineer minded so these different litered engines are baffling me ; of late ! For some incorrect reason when the 2006 Concept came out with the 425 HP/ 6.1 Hemi engine, I just thought it was the 426c.i. engine ! I hear about a 392cu Hemi ,, as well as the 6.4 and now from Fooseland the use of a 7.0 in their Challenger project ! I just ,incorrectly, thought that DCX was still making all of the original engines and converting to liters: but I've just looked at a converter and see that ... the 6.1 is really a 372 c.i. .. a 5.7 is really a 348 c.i. engine ..ok... now 383 converts to a 6.278 or 6.3 [ to round things up ] ..ok and yes 392 is 6.4 [ 6.42 liters] so I understand the 426c.i. is 6.98 or 7.0 so where is the Mighty 440 c.i. engine or a 7.2 liter ? The old 318 cubic inch workhorse equates to 5.2, and am wondering if that is still being made ???

[PhantomR/T]

they stopped making the 5.2 in 2000ish

[Dutch]

I think the easy answer to your question is peer pressure. They probably save a nickel on parts by sharing commonality with the rest of the world.

There is a real difference, though, in that new engines such as the 5.7L are truly metric engines - their bores and strokes were determined in mm rather than inches, so it's correct to refer to them in their metric sizes. You will note, however, that the 5.7L is actually 345 c.i., not the 348 you get from the conversion.

Because old engines were designed with standard measurements, like the 4.25 bore and 3.375 stroke of a 383, it's correct to refer to them by their cubic inch numbers. Chrysler's use of 5.2L and 5.9L for the 318 and 360 was just marketing.