Larry, part 3 apparently has another page. It says continued on page 12 at the end of the second page. Thanks to Devon and you for re-posting these.
I think it might be the 67 heads and possibly some of the early big port heads that are prone to cracking. I had a set of 67 big port heads that were cracked in the area between the valve springs and valve cover lip above the center 2 exhaust ports. I have worked with and looked at multiple sets of 68-69 heads and not witnessed any cracking. However I always say, never say never because anything is posible.
Way back I had a set of 67 early big ports done up, pretty well to the article the above, and they flowed 283 @28" on intake. Made some pretty good power with an old SP 4 Lunati cam (253/270) but the sinking of the exhaust valve .030 deeper than intake (per article) was a mistake and played havoc with the valve train geometry. I used KB 107 valve springs set at 110 seat pressure and never had a cracking issue. Tom
