If you have the drive plate or flywheel on the crank I'd use a big screwdriver in the flywheel teeth to hold the crank. As far as a block of wood between the lower end of a connecting rod and the block, or even the journal and the block I just don't think you and a two or even three foot bar will hurt anything, unless your the lad I saw carry 5- 98 lb bags of cement. If thats the case I don't know and sure don't want to give you any bad advice. kotzy