cooling trouble

[lilhows340]

Just finished 73 scamp block cleaned & honed . New rings bearings timing chain water pump recorded rad Mr gasket t'stat. 73 318 with newer after 79 4 barrel intake. The problem is when the t'stat opens with cap off it pushes coolant out and turns into a gusher when engine is shut down. Run good normal temp with cap on but when it is shut down pushes out over flow. Any ideas would be appreciated. Have moparfest show today will check back after 6.
thanks Jeff

 

[George R]

Sounds like air in the system turning to steam and expanding. I always start a new motor without the thermostat and run it like that. When you get time in the future, install the stat.
Good Luck.

George

 

[Snake]

also drill a small hole in your stat if there is not one.