Looks Like someone either over tightened the vacuum fitting or forced it out too hard!
It's a great manifold. I paid $80 for it.
I cleaned it up -Painted it the same color
slightly shiner. This crack is very small
Oh! It's like someone forced an oversized
fitting or tight fitting onto threads.I'm sure now thats what happened because the 2 holes at rear are the same size. the higher up one (The cracked one) is slightly bigger .(thread tape will correct).Threads are ok.
Its not a normal flaw or because of the manifold.
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