[ford38v8]

Mike, that makes sense, but I'd still like to see inside a manifold to see if an internal mod could benefit.
GM reported a short while back that the insulating block wasn't as effective as hoped for.
If the internal cavity is one large open chamber, perhaps an insulating filler could be used at the top for an additional reduction in heat transfer to the carb. No magic bullet, but a heat reduction here and there...