LA 340 block crack in deck
I don't think that's a core plug.
Looks like a datum target, or someone machined a flat for some reason. Pictures of other blocks with the same boss configuration don't show the flat spot.
The flat spot left a thinner wall adjacent to it, could have been clamped on for some work or the thinner wall might have helped initiate a crack. Hard to say. I don't think that boss has any oil in it (it doesn't intersect the cam tunnel the same way as the head-oil hole does).
It's probably a non-issue, but it's tough to say. Cracks have a way of growing, so I'd try to grind it out. What's there to lose? It'll have to get ground on to repair it too. It looks like other (maybe later vintage?) 340 blocks had those bosses reshaped to a smaller profile.
Here's a picture of a block without those big bosses:
and one with (but no spot faces on the bosses):
I don't think that's a core plug.
Looks like a datum target, or someone machined a flat for some reason. Pictures of other blocks with the same boss configuration don't show the flat spot.
The flat spot left a thinner wall adjacent to it, could have been clamped on for some work or the thinner wall might have helped initiate a crack. Hard to say. I don't think that boss has any oil in it (it doesn't intersect the cam tunnel the same way as the head-oil hole does).
It's probably a non-issue, but it's tough to say. Cracks have a way of growing, so I'd try to grind it out. What's there to lose? It'll have to get ground on to repair it too. It looks like other (maybe later vintage?) 340 blocks had those bosses reshaped to a smaller profile.
Here's a picture of a block without those big bosses:
and one with (but no spot faces on the bosses):
