There are lots of sites out there that offer products for MAKING
silicone/urethane molds, but very few talk about products for CASTING
the product. Those that do, have not returned my e-mails. Maybe
because I don't want to buy 55 gal. drums of their product. Can
anyone
offer some help on who might carry a product that will satisfy my
requirments? Thanks for any ideas.

www.smoothon.com has a decent set of how-to articles online that show
how to make a mold and how to cast using the mold. They also sell rtv
and polyurethanes but I don't know if they have any that go to 350F. I
do know that when I called with a quick question they cheerfully passed
me to a guy who knew the answer. I think you will want more like shore
70A for air filter plumbing, but that's just my guess. www.mcmaster.com
sells a set of test pieces about 1" x 2" x 1/8" covering shore 40A to
70D (with some gaps) that is pretty cheap.

--
Regards,
Carl Ijames carl.ijames at verizon.net