Re: 400 sbc question about running hot?
Cub not all 400 blocks are alike. Some have additional cooling holes in the decks and I'm NOT talking about the steam holes. Ligenfelter addresses this in his books and recommends adding the 7/16" cooling holes at the outer deck surfaces between and below the boresof the middle cylinders if yours doesn't already have them. This helps provide additional cooling to the siamesed exhaust ports of the cylinder heads, the hot spot. Also Ligenfelter, Yunick and others suggest tapping the large 3/4" coolant holes above the bores on you block deck surfaces with a NPT tap and installing Moroso deck plugs. While they arguably help strengthen the block deck surface they primarily restrict the volume of coolant that is allowed to move up into the heads at the intake side. This isn't where it's needed and also can prevent adequate coolant to the rear cylinders. The deck plugs reduce the hole from 3/4" to 3/16" and divert more coolant to the rear cylinder water jackets before it's allowed to move upward. If you do this mod, it's eary to do, go slow with the tap, keep testing the plug, you want the plug to tighten BEFORE all the plug is run down into the deck. Leave a slight amount above the deck and it'll be machined flush when the block is decked.
Another recommended action is to insert a brass plug into the bypass port on the passenger side leg of the water pump. Many aftermarket pumps come with this plug already installed.
"..............what, and get out of aviation??"