"A V-8 engine is much smoother because it has eight evenly spaced EXPLOSIONS instead of one big EXPLOSION. Another reason is starting torque. When you start a V-8 engine, you are only driving two cylinders (1 liter) through their compression strokes, but with one big cylinder you would have to compress 4 liters instead."
From howstuffworks website...
"A V-8 engine is much smoother because it has eight evenly spaced EXPLOSIONS instead of one big EXPLOSION. Another reason is starting torque. When you start a V-8 engine, you are only driving two cylinders (1 liter) through their compression strokes, but with one big cylinder you would have to compress 4 liters instead."
http://www.howstuffworks.com/engine6.htm