conjunctions - 'if', meaning 'even if'. Why would ommision occur in some cases?

From Michael Swan's Practical English Usage 261.10: If, meaning 'even if'

We can use 'if' to mean 'even if'.

I'll finish this job if it takes all night.

I wouldn't marry you if you were the last man in the world.

I wonder if we can omit 'even' in any other 'even if' clauses. If not, when is the omission acceptable without causing any misunderstanding?