So I pulled apart my Z6 to prep it for a vitara setup and when I pulled the crank out of the block I found these small cracks under cylinders 3 & 4, should I trash this block? I don’t want to dump a bunch of money into good parts just to blow a hole In the block, thanks in advance

 

Those look like casting lines. You can have a machine shop dye test it to see if it's truly cracks or just casting remnants.

You might be sweating over nothing or you might have found something, machine shop will tell you.

https://www.hunker.com/13416275/how-...with-magnaflux

 

Those are definitely artifacts from the casting process - nothing to worry about. If you look closely or feel them, they are actually raised above the surrounding surface.