I don't have any knowledge of the magnum heads, but I've heard that they are prone to cracking next to the valve seats, my question is if they crack next to the valve seats won't this only get worse? Will the cracking cause the valve seats to come out? Also I just looked up what edelbrock performer rpm heads for a sbm would cost and was surprised to see that they are around $200 a pair cheaper than promaxx heads.
ive heard that the later magnum heads had this problem fixed im not sure if that is true or not but all i did was pull the heads and run a razor blade between the seats and if there were no cracks i ran them.
