NCrunch will automatically apply a timeout of 60 seconds to each test (by default). You can change this by adjusting the configuration on your test project, 'Default Test Timeout'.

However, a better way to do this is to assign sensible timeout values to each of the tests individually. This can also help with tools other than NCrunch, as it can give some level of certainty that the integration tests won't hang and block up big test runs (i.e. on a build server).

I recommend having a look at creating your own custom engine mode for the integration tests. Assuming the integration tests have a particular category, you can create an engine mode that will automatically run all tests outside this category, then run the integration tests manually.