I agree, call clifford and see what they say. Tell them exactly what you told us. Let them know you bought it 8 months ago when you started your motor rebuild and just got finished with the engine and went to start it and discovered this problem. Don't stick it to Jim Carter. If clifford doesn't resolve the problem then purchase another manifold directly from them and then swap it.
I can't see them not changing it out for a new one as it definitely sounds like a manufacturing defect. If they don't want to let them know they have over 20,000 potential customers waiting to hear back on how they resolved the problem.
