From investigations by enthusiasts who where concerned about the 2.7l being stamped/embossed onto there engine block, it would appear that the 968 engine uses the same although modified block as the previous Porsche 944 2.7l model also used by the Porsche 944 S2 3.0l model.
Here are the details,
All 944s upto 1989 had bores of 100mm.
From 1989 onwards - 944s including 944-2.7, 944S2 and then 968 had a
bore of 104mm.
From the 924S through to the 944S the stroke was
78.9mm.
From the 944S2 3.0l (1989) to the 968 the stroke was 88mm.
So the combinations appear to be,
100 x 78.9 giving 2479.038cc - being 924S - 944 - 944S
104 x 78.9 giving 2681.327cc - being 944 2.7
104 x 88.0 giving 2990.580cc - being 944S2 and 968
Making the assumption that we have a uniform cylinder,
the calculation is,
pi x (radius x radius) for the area,
then multiply the area by the length of stroke for the volume,
then multiply by the number of cylinders.
Example bore = 104, divide by 2 for the radius
(104 / 2 = 52),
square the radius (52 x 52 = 2704),
multiply by pi (3.142 x 2704 = 8495.968) for the area,
multiply the area by the stroke (8495.968 x 88 = 747645.184),
multiply by the number of cylinders (747645.184 x 4 = 2990580.736),
divide by 1M for litres or 1000 for CCs. = 2990cc.