Interesting you mention delrin, Gord. I have a square foot by 1/4" thick piece sent by a friend (not a stovebolt guy...another friend). As it turns out it is only fairly resistant to gasoline. Plus it is not easy to work with. Teflon/PTFE is a possibility. Rings of it are available, however I haven't found any in the size I need. There are also a couple of other plastic compounds and there is always nylon, although I wonder if nylon would perform any better than the o-rings. Part of me doubts it.

Jerry...does that stuff add any dimension or thickness? As I figure it, I have around .002~.0025" to play with between the piston and the bore.

Jon...I agree with you and others the Carter one-barrel is a better design from a few important points of view. Really it seems to me the Rochester is in ways fundamentally flawed and I'm surprised they stayed with the design knowing the mistakes (and it is clear to me they did). I wish I could have found more of their bulletins. It isn't so much that I'm enamored with the Rochester. As much as anything I want to see if answers can be had. I'm not familiar with the Teflon strips Holley used. I'll try to give you a ring next Monday or Tuesday.

~ Jon
1952 1/2 ton with 1959 235 | T5 with 3.07 rear end