So I'm getting ready to flush out my 292 y block which has sat for over 15 years. Does the engine coolant to heater come out of the intake manifold and back to the water pump or vice versa. Also I've read that there are coolant drain plugs or valves in the block, can you guys explain which ones they are. Thanks.

 

The WP draws from the bottom of the radiator and coolant is expelled out the thermostat housing allowing coolant to migrate, by gravity, top to bottom. The coolant path for the heater goes out from intake through heater, and back to pump. There are two drains on the block, about the middle of the lower part of the block on each side. Sediment collects at the base of the cylinders, after removing plugs it may be nessesary to poke something into the passages (i.e. a small screwdriver) to initiate the drainage.

 

Thanks for the detailed description. The reason for my asking was I installed a filter in the heater circuit like we do on the powerstroke. It's working quite well to get the last little bits of crud out of my recently derusted cooling system.