The crank moves a little and defeats the impact pulses. If you got it off with an impact it was already loose.

 

I have to disagree. The impact of the gun is faster than the crank can react so the bolt will absorb this force, and the bolt will come loose.

 

All these methods obviously work. I just mentioned what I like best. Never had a loose crank bolt, just good impacts. Even pulls them with locktite.

Ive done the rope thing on SB chevs to swap valve springs and seals. The air pressure method too.

Never wanted to put liquid in my cylinders to hold it. Kinda scares me.