for stubborn crank bolts I used the socket/breaker bar combo. see what way the crank turns when starting/running. stop Eng, put socket/breaker bar on bolt with the bar leaning on the frame opposite of the crank pulley revolution. tap the key and (if the breaker bar doesn't fall off) it usually loosens the bolt right up. My first battle was my 72 olds 350. i had so much torque on the crank the car was almost lifting off the ground, after most of the day battling that one bolt my uncle told me the crank trick, it worked instantly.
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