Does removing the rad hose on the engine
side drain the block?

 

No
There is one drain plug on each side, center of the block, just above the oil pan rail.
You must use these to properly flush the system.

 

I tried unsuccessfully to move one of those plugs, and the other one I think is behind the starter motor, so I reverse flushed the system a couple of times (using a kit made by prestone) and ran water through the running engine until it ran clear. Haven't flushed in a few years. Thanks for reminding me about something I really don't want to do! (Yes, I drain and save the engine coolant twice before flushing)

 

How often should you do this?

 

How do you reverse flush

 

You should really do a super cleaning once as long as you do proper maintenance. It's not an easy task, takes all day, proper acid and a lot of water. Repeated flushes back and forth until no debris comes out. Must be done initially with the rad disconnected.
If the plugs are tough to get out, heat and cool them, smack them hard with a good drift and hammer and use a 6 point socket preferrably with a 1/2" drive ratchet set. Drill them out if need be, but it should be done. Replace with hex brass plugs.
At most the ignition wire shielding can be in the way of the plugs.
Here is a pic of about 10% of what can come out. It's really pretty normal for an engine of this age.
Thereafter, just drain the fluid, rinse with water and replace with new antifreeze and distilled water yearly. Less than 20 bucks. Well worth it.
To reverse flush, I have a brass adapter that goes in the intake maifold heater port and also these block ports connected solid to a garden hose, let it overfow the top of the tstat opening and let drain out numerous times. Same with the rad, from the bottom then the top numerous times.
Then plug up and connect and drive with the cleaning acid, then the flushing process all over again. It ends up like new inside.

And if you are installing a new radiator this debris can plug it up in no time, especially aluminum radiators that have smaller tubes than brass rads. Do the good cleaning with the old rad in there, then install the new one.

 

It's called a bidet (French)

 

Prestone also make "Radiator Cleaner", which has chemicals that will dislodge the lime deposits out of the radiator fins. You must follow directions and it takes 2-3 drain/fill cycles (just water and the cleaner) and some time running the car, but it does a good job of cleaning out a system that may have some 'gunk' in it.

 

I think I used this:

http://www.prestone.com/products/print/461?popup=1

 

Anyone using a water less coolant. This product might be the way to go since it will last the life of the engine. http://www.evanscooling.com/