I always lock the engine with two pairs of vise grips on the flywheel- - - -one at each side of the opening in the bottom of the bell housing. It's also possible to clamp the fan belt in such a way to immobilize the crankshaft.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!