I think your ok Dirka, its only in high compression race engines have I seen the problem. Despite the weaknessess of the 400 block it is my favorite engine all around because it is so amazing. I built a 406 with ported Brodix heads and GM Block with a solid lift cam and 10.5 to 1 compression. In a 3200lbs car with a glide and 5000 stall converter it ran 10.60s with a best (in good air) of a 10:55. It ran for 3 seasons every weekend and no problems. Took it out and change compression to 14.5 to 1 and a roller cam, split the cylinder in the 1st pass!!!! Awesome engine tho.
Chris