BlockMesh checks
 

If I know that my blockMeshDict is perfect; let's say I tested it using lesser number of nodes in all three directions and everything was fine, then is there anyway to skip all checks when running blockMesh?

The reason I ask is because I'm trying to do a mesh refinement study and the resulting mesh will be around 56 million cells, I would like to cut down on any time involved in checking.

If this is possible, can someone tell me which lines to comment in the source?

There is very minimal checking
 

There is very minimal checking during blockMesh and all in the polyMesh constructors. So unfortunately, there is no easy way of reducing the blockMesh overhead (although it certainly is possible).