-
You can manage & track your card collection and decks once you create an account and login.

What happens if I have 5 cards in hand when Crankcase attacks but during the battle I go down to 4 or fewer cards in hand? Does Crankcase keep the attack bonus?

Yes. All that matters is that you had 5 or more cards in hand when Crankcase attacked. The attack bonus will last until the end of the battle, even if the number of cards in your hand changes.
Source: Wizards of the Coast (2020-05-09)    【Link to Ruling】
Tags: Crankcase, Data Collector