Is this a crack? Check it out!
 

I am starting to put back together a bent rod engine. It has been fully machined and now has forged pistons and rods (and all the machining needed to get her going again).

I noticed that there is a strange hole near at the far corner of the bottom of the block (near the crank). The shape of this hole looks to me like a crack or rust opening. I don't see it as something that would cause any catastrophic issue, as it is just a mounting hole, nothing vital. But it still has me worried.

1) Is this normal or is my assumptions correct that this is an abnormal hole/crack.

2) If it is abnormal should I:
a) Leave it alone. I repainted it with engine enamel so that should stop any rust or maybe further issues
b) Fill it with JB weld or other fix approach?
c) Other?
https://cimg2.ibsrv.net/gimg/www.mia...64f47ffff5.jpg
https://cimg3.ibsrv.net/gimg/www.mia...e9386e5282.jpg

Perfectly normal on BPs.

I was expecting to see nsfw content