Apparently, I am the only one that reads CarCraft. They have a stroked and poked 318 article in it RIGHT NOW.

4" bore 318 is not uncommon, but as said t is sonic tested first. BTW, all you recommending a sonic test, what's you minimum wall thickness recommendation?

(funny how everyone hollers sonic test, but no one says what you need, methinks Polly has been around).

They say there are no such thing as a stupid question.
They say there is always the exception that proves the rule.
Don't be the exception.