What does node --nocrankshaft do?

What does running Node.JS with node --nocrankshaft actually do? Is there any documentation on these types of v8 settings options in node?

This disables the Crankshaft compiler.

...By using aggressive optimizations, Crankshaft dramatically improves the performance of compute-intensive JavaScript applications - often by more than a factor of two!...

Have a look at: A New Crankshaft for V8

For more details: a closer look at crankshaft, v8's optimizing compiler

Is there any documentation on these types of v8 settings options in node?

The --v8-options flag can list all the settings related to V8:

$ nodejs --v8-options

Options:
  --use_strict (enforce strict mode)
        type: bool  default: false
  --es5_readonly (activate correct semantics for inheriting readonliness)
        type: bool  default: true
  --es52_globals (activate new semantics for global var declarations)
        type: bool  default: true
  ...

The list contains all the flags related to V8, a short description of what each flag does, type information and default value.

The list is also available online here: https://github.com/joyent/node/blob/master/doc/node.1. Most of the parameters of this list correspond to V8 flags.