The 340 is out....again.....

RAMM said
Like I said--not the culprit. I'd bet $$$ on the main feed passages not drilled the correct diameter to the full depth. J.Rob

You would surely have a better handle as to why this happened but I still have to wonder about the history of the block and was there ever a problem prior to rebuilding it? Could a passage have gotten clogged from machining debris?

JW