Engine is a 390 +.030, ~450hp, 6000rpm, hyd roller, hot street deal. Going in my 67 Fairlane.
I know the blocks will crack form the mains to the cam tunnel, but never heard of one cracking from the cam to the oil galley. It doesn't make sense to me that you have a 1/4" hole feeding the cam bearing, then feeding a 5/16 hole to the main. To me, that makes the 1/4" hole between the cam and main oil galley a restriction to the main bearings. It would be better if the cam bearing holes were 5/16 and the main saddle holes were 1/4", but it is what it is. I have a Canton pan, pickup and windage screen, HV pump, ARP shaft, will set bearing clearances accordingly.