[Trochoidal]

The one thing that had me scratching my head with your oil spray was the fact that it was all over the place. It’s not like it was isolated to one area. You clearly highlighted the wet gaskets on the intake manifold. They were what I’d call “sloppy” wet. Too much considering this is a fresh build and using (I’m assuming) stock hardware.

You could always do some simple math to confirm those holes were drilled and tapped at the right depth. (Also as you said you’re going to check).

The other night when you posted about thinking the runner gaskets were leaking, I was thinking feeler gauge around those ports. However that gap could be small enough that a feeler wouldn’t pass between the gap and still let oil out.

So the machinist in me has a question. Were the chamfers on the intake manifold bolts “shiny”? (Usually only happens with steel on steel contact) Did the bolts have aluminum deposits from the bolts bottoming out in the head in the event they were tapped shallow?

As for the oil coming in through the rocker stud I’m thinking that would only happen when you had vacuum.

Another observation I had was the picture of the tap in the hole. That was a 4-flute hand tap. That style tap pushes the chips into the bottom of the hole. If they tapped them “under power” the tap would not be able to achieve enough depth because of those chips being in the way. This of course would cause the tap to break if there was probably more than 1 pitch (1turn) of the tap after the interference. So if they hand tapped the holes they would have stopped threading the hole when that tap bottomed out. This would cause a shallow thread.

I’m speculating at best but your theory of shallow tapped holes sure seems very plausible.