Head gasket

There is only a limited space for coolant to flow, the water jacket in the block dissipates the bulk of the excess heat, there is enough circulation to cater for the heat in the head, the use of a good quality coolant will stop any sludge from building up and blocking these ports, also if you look at how many transfer ports are in the heads, combine them, this is a fair size for water to circulate.

Mark (mhpautos)