Is a four bolt main crankshaft the same as 2 crankshaft?

No, a four-bolt main crankshaft and a two-bolt main crankshaft are not the same. The number refers to the number of bolts holding each main bearing cap to the engine block. A four-bolt main setup generally indicates a stronger, more rigid crankshaft mounting, better suited for higher horsepower and torque applications. A two-bolt setup is simpler and typically found in less demanding engines.