New engine
 

I'm into a 72 Grand Prix with a freshly built 71 455. Intake was leaking at the exhaust crossover. Pulled the intake to replace the gaskets and get it sitting correctly. Only one bolt torqued. The man that built the engine has since retired and was a professional engine builder. I can't believe that he missed the cracks in this head, casting 66. Owner dropped off a pair of 96's this morning that I'm going to have rebuilt to go on the 456.
I've gotten used to go behind other shops work to correct things.

What you’re seeing is normal, it’s simply the parting line where the two halves of the mold come together. It’s quite common actually.

Those are not cracks, your heads don’t need to be replaced. Just use a small dab of ultra grey sealer to prevent oil from migrating into the intake ports.

That one runs clear to the pushrod tube. One port (I tried to get it in the picture) had been welded. The other head is perfect.

No matter what the 96 heads will wake up that 455 with a nice 1-point bump in compression.

I have seen many Pontiac heads with cracks in this location. Most are superficial, easily repaired with a bit of epoxy.

Probably one of the few practical uses for JB Weld.