Engine Mount Washers

[NE Cub]

I seem to recall there being thin, phenolic washers between the engine mount and the firewall where the engine mount bolts to the airframe. Is this correct and were they supposed to be on both sides of the firewall ie. between the airframe and cabin side of firewall as well as between the engine mount and the firewall? What is their purpose?

George

 

[huston marlowe]

 

[NE Cub]