how many Crankshafts are in a V-8 engine?

All modern engines, regardless of cylinder count and layout (V, in-line, flat) have one crankshaft only.

As for camshafts (if that is what you meant), a V engine may have from 1 to 4 camshafts, depending on their position.
Only ONE crankshaft in ANY V-8 engine. Depending on the cylinder head configuration, there could be one, two or four CAMSHAFTS.
One. All 8 pistons are connected to it. As they move up & down, they spin the crank kinda like pedaling a bicycle.

Now as far as camshafts go (which open & close the valves), your typical V8 will have anywhere from one to four cams. Most modern GM & Chrysler V8s have one cam, Ford will have either two or four, and most import V8s will have 4 cams.
Only one crankshaft per any engine however you can have multiple camshafts

:sohc single overhead cam

dohc double overhead cam

Source(s): auto body tech and shop owner
Just one, dude! And as many as four overhead cams depending on the engine.
good read on V8 engines.

http://en.wikipedia.org/wiki/V8_engine
1. camshafts are more.