After reading the entire thread here...I admit
to having the same problem. My setup is just a
stock 360 engine with a Weiand dual plane manifold. A 3 year old Edelbrock #1406 600 cfm carb (junk IMO) and ceramic 1-5/8 headers. The car starts fine when cold....has NO spacer or shield on it....
when just warm, it very hard to re-start. This is
even in 50-60 degree weather as others posted.

I ordered (just about 2 hours before reading this thread) a 1/2" wood spacer and an aluminum heat shield kit from Jegs. I hope this helps out...and if not, I'll try the return line trick I read on here too.