My .030 over 400 block doesn't have an overheating problem. I personally think that alot of the overheating porblems assiciated with the orginal 400 is those short rods and all of the extra friction on the cylinder walls created by them. Just my thought on it. I know of quit a few folks that run 400's that don't have any overheat problems. I don't even have both sets of steam holes drilled in my heads as per edelbrock and no problems with heat.