I am replacing everything coolant related in my 69 firebird conv 350, (water pump, radiator, hoses, thermostat, fan, etc) and am having problems removing my coolant inserts that I was advised to replace as well. The drivers side required a great deal of fighting to get out, and it looks like it will be fun to get the new ones back in. Besides running warm, the motor appeared to have some small coolant leaks around the botton of the intake manifold and near the timing chain cover.
Appreciate anyone's input or advice in doing this work.
You could use some heat on them to loosen. And when you put the new ones in, freeze them to shrink and make it a little easier. Be very careful not to score the contact surface on the block with the tool you are using. If you put a deep scratch in it, it may leak later on. You could use a dent puller to remove them.