All of the X blocks were cast at 3.91 bore. They are actually under that by a bit. My last block measured 3.840 rough bore. Second, before they sonic test it, they need to bet ALL of the rough bore out of it. Meaning, they need to get it in the boring mill and cut the bore until it's clean. Then you can get a real sonic test on it.
I've had 3 X blocks and worked on a dozen or so more. I've never seen one that wouldn't go 4.100 easy. But you can't tell that with a rough bore.
As for the main line...I have no idea how the bores can be that far off. That's ridiculous. Find a different shop if they are doing the sonic test on a rough bore.
