The current "5.7" Is more like 5.65 And is 345 CID, not 343, or 353, or 348, or 355..... Its 345, PERIOD.... Yes the sticker says 348, I was wrong when I used to go by that.

 

The current 5.7 is realistically 5.65, and has a CID of 345, Not 343, or 350, or 348, or 353, or 355.. Its 345, Period.

I used to go by the sticker also.

 

5.7 Hemi
Bore: 3.92"
Stroke: 3.58"

Displacement = pi x (0.5 x bore)^2 x stroke x number of cylinders = 345.64848860416 cubic inches (assumes pi = 3.14159)

So it's 346 CID, really.

 

Via Allpar,

Different Dodge listings mentioned 345, 353, and 354 cubic inches as the engine size; but Chrysler seems pretty sure it's a 345, though as Jack pointed out, the bore and stroke times pi times the number of cylinders = 353. Patrick Clement, however, tried an on-line calculator and found 345 cid; and the mystery was resolved by Derek, who wrote "Ahh, the correct formula is pi x (bore/2) squared x stroke. This is because bore is a circle and area of a circle is pi x r squared! Try it and you will find 3.92/2 = 1.96; 1.962 (3.8416) x pi= 12.0687 x 3.58 stroke =43.20 x 8 cylinders = 345.6. I guess the engineers at Mopar can calculate displacement. Anyone that can put a man on the moon....well if you've ever ridden in a 426 hemi, you know what I mean. [Gaymon Wright points out that his window sticker lists the Hemi as being 348 cid...and Jim O'Donnel wrote "Your equation for determining C.I. displacement (345 C.I.) is right on (correct). The 353 C.I. displacement comes from taking the circumference of the cylinder times pi times the depth/stroke i.e. ((2*r*pi)*stroke) which equals 353 C.I. as opposed to doing what you did which is taking the area of the cylinder times the depth/stroke i.e.. ((pi*r2)*stroke).]

Final notes: Mark Strode -

If you use the SI units (millimeters) for bore diameter and stroke to first calculate displacement in cubic millimeters then divide by 16,387.064 (which is the exact number of cubic millimeters in one cubic inch) you get 345.055 cid.

This is the most accurate way to do the calculation because the Hemi is a "metric engine". Rounding the bore and stroke off in english units (3.92 X 3.58) then doing the math adds a little error.

Gary Watts -

This is all really simple if you just remember that cid is a volume measurement or inches cubed (in x in x in). When you take the different formulas and include the measurements, you will see that only one:

pi * (r) squared * stroke

gives us inches cubed because our radius measurement is inches (squared) and stroke is inches. This gives us inches cubed.

The other formula, 2 * pi * r * stroke, only gives us inches squared (which is area, not volume) This formula actually gives you the area of the cylinder that the piston covers in its movement. In other words, if you cut each cylinder from top to bottom and rolled it out to look like a rectangle and measured the length times width.