Originally posted by Gunslinger09
Heres an easier way courtesey of Speedomotive INCs web page.
BORE X BORE X STROKE X .7854 X # CYLINDERS =
CUBIC INCH DISPLACEMENT
That works too but the .7854 in this case gives you 402.1248 Cubic inches. So its all fairly relative.
Technically there is no way to tell cause Pi is an unknown value, you can calculate it too 200 decimal places and it still keeps repeating.
Technically you could use 3.1415926535897932384626433832795 for pi which yield 402.1238 ci
However you should only use the same number of decimal places that you have accuracy in your machine tooling. For example the bore is 4.00 cubic inches but could be 4.0004 or 4.00065 or some other variable beyond your machining tolerances. So really you would have to know to what tolerance GM bores are measured.