Remove crank bolt - engine is free standing on garage floor ??

[Jccck]

The key with undoing any bolt/nut is impact.
You can't just hold it down, and swing off it.. You need to anchor it as solidly as possible, so when you yank on it with the breakerbar.. ALL force is put into the fastener, and not absorbed by whatever's 'not' holding it secure.

I like the 4x4 idea, make up something that will utilise engine mount locations and have a decent length of bar off the end.. With the 4x4 parked ontop of the bar the engine shouldn't move.. Stopping rotational force of the block is difficult, but by extending something out the side you get the advantage of leverage =)

Helps if you have a welder, a grinder, and a drill.. Haha.

With the breaker bar, if you try and apply leverage slowly you'll tilt the motor. With a breaker bar, get a large hammer and give it a massive smack. May take a few times but what you want to is overcome the friction holding the bolt in tight. Once you get it turned a bit, you should then be able to rattle gun it out. Give that a go!

Good method! They say 'crack' bolts for a reason.. Not 'bend' them.
Sudden impacts work better than applied weight any day