Where are hemi heads prone to cracking?

I have a 392, and I think the heads may be cracked. Where are they prone to cracking? They are ported, o-ringed, oversized intake valves and lived for quite a few years on a pulling tractor. Thanks.

-Jeff

 

Check from the valve seats to the plug hole.
that's where mine cracked.
r

 

That's kinda what I figured. What about in the spring seat area's or around the valve guides? Thanks

-Jeff

 

bttt

 

In my linited experience, I've not seen any crack in either area but it sounds like springs were involved. Would too stiff of a spring cause it to crack there?
r