BX23 head DIYer, machinists?

[tshep]

Here are 3 pics of my 3 different combustion areas.
Each seems to have....
A same size line, then a stake point, middle

flute of precombustion chamber?

OR

exactly the same crack.

Assuming these are assembly marks, what is a good homebrew/DIY crack detection method?
Or, not finding any, do I just assume it was the gasket?

I had oh-so-slight bubbling in radiator, 22 years old.

 

[dodge man]

Just a guess the mark is where they are suppose to stake it in?

 

[tshep]

I suspect it's to align the circular insert that closes the pre chamber. They all curve off a bit at the top - as though the guy was aligning his scribe, and pulled it down against a 'jig' - straighter at the bottom.
The inserts all sit proud a bit - how would one surface the deck?