Hey , just a thought , can you stuff something like a welders mit or something that won`t catch on fire between the rear carb and manifold when the conditions are right for the problem ? There must be some way to temporarily isolate the carb from the manifold . I remember reading about this somewhere that the manifold temperatures can affect the carbs on a b16 and it seems like I have seen a spacer that is thicker than the one you are using . How thick is the spacer you are using because I think I may have a couple that are thicker . Nice resto . Wish my 58 looked that nice . Larry