Never ever use cinder blocks.
When I was younger, in the '60's, this was common knowledge. Cinder blocks will fracture and fail all at once as in causing a collapse. There were many stories of people being killed or maimed by cars that fell on them because they had used cinder blocks as jack stands.
Cement blocks may be a little better but they were generally avoided also.
Seems we used to do a lot more with a lot less in those days.
Railroad tie lumber is OK. Use it often even today.It is used in boat yards to hold the keel of boats. I have seen even bigger stuff than railroad tie lumber in boat yards.
Had a 1954 Cadillac convertible on jack stands for about 5 years in front of the house I live in. My house mate gets some pretty interesting projects. All he was doing was some refurbishing of the interior and exterior trim. The county inspectors who like to hassle us for having too many junk cars and trucks around were pretty nice those 5 years. Now that it's gone we have to clean up a little more. Pretty funny when i think of it.
