The timing for this thread couldn't be better. I'm was just in the process of reassembly when this thread started. Didn't even know "gland rings" were a thing. Since my manifolds are new (400 miles on them), and after reading all the comments, I decided that these rings are a good idea so I made some up on my lathe. Henry Ford wasn''t one to spend money where it wasn't necessary so if he thought they were not needed, he wouldn't have included them. Plus, the concept seems sound to me. Time will tell I suppose but pretty easy to remove if, for some reason they don't pan out. The reports of them ending up in the muffler are baffling to me. Unless they had a WAY too big of gap, it doesn't seem possible for them to come out that I can see. I WAS going to just make them solid with a snug fit but decided to make them a few thou oversize and cut them with a hacksaw to give me a little flex for ease of install and still have a snug fit. Ended up with about a .0010 gap. I read somewhere that without a gap (1/16" IIRC) they will expand and buckle and end up in the port. I'm not so sure about that since it seems to me that any pressure would be equal (due too them being round) and if they DO buckle it would be at the gap. If this happens, I can always make new ones, either with more gap for expansion or no gap (Make them a snug fit without cutting them). Anyway, thanks to the OP for starting the thread and thanks to all that responded.