Z_on_TE37's

I just dropped off my sr20det at the machine shop to get some machining done for my engine build. As he was looking over the head he noticed two hairline cracks starting at the spark plug holes going towards the valve seats. Does anyone have any first hand knowledge on whether this is common and safe to run or if it's going to end up as bad news. I can't find anything other than one post about the same topic and that wasn't helpful. Please help me out here guys!