I used to wrap a rag around the rubber slip grip of the turning lever/pipe on the engine stand....I'd put the rod big end over the end with the nuts loosened to last 5 threads and then use a hard plastic head hammer to tap each bolt on the nut while slight pulling down on the rod till it separated. I did that for 5 engines before I got sick of it...lol
I'd do all 8 at once and then lay them out with their caps for bearings to go in etc...
The vise idea came about and that was end of hammers.
