Hello baldy, this techinspector1. I used to be a member here, with over 12,000 posts. I don't post on here any more, but just happen to be visiting NTFDAY (Ken) in Springfield, Missouri. Ken asked me if I would field this question and so yeah, I'll give it a try.

I understand that you have had it apart and had it apart and had it apart, but did anyone record any dimensions? If the fellow at the machine shop was one of the people doing the examining, he might have no reason to find anything wrong, because he did the cutting and does not want to anty-up for the fix.

There is no doubt in my mind that there is one or more cylinders where the gap between the intake manifold and the cylinder head is thicker at the bottom than at the top, allowing oily air to be pulled into the head ports from the interior of the block.
Have you examined the intake gaskets which you have removed from the motor? Did you check the thickness of the "pinch" all around each and every port and record the numbers that you found?

Has the block been decked? How much in thousandths of an inch. Do you absolutely know that the block decks are separated at 90 degrees? Could the included angle be 89 degrees or 91 degrees?

Here's what you need to check what you have......
Intake Angle Gauge: BHJ Products, +1 (510)797-6780

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