I put 23K trouble free miles on a 216 sans those rings..... When I R&R'ed the head the originals were toasted beyond reuse so I installed the manifolds without them as I really wanted to see if the engine would run. It did and the need never arrose (?) for said rings.....
I did install those rings on my 235, haven't put any miles on it yet but it's getting oh so close...
I don't believe those rings will stem an intake or exhaust leak, IMHO they are to keep the gaskets inline whilst installing the manifolds, IMHO ofcourse LOL...
