vegabond

I need some help on some SBC heads(sb2.2, 18 degree) both styles of heads are getting cracks in between the center 2 chambers i.e. (between the 2 siamese exhaust vavles). Is it because of the steam holes that are drilled parrelle to the deck between the outer water jacket and the inner one(there on bowtie blocks which are siamese cylinders)? If i grind them out and weld the cracks up do i need to redrill the steam passage? Just didn't know if the heads would be O K without that passage? Thanks in advance for the help---Steve