<<  In my opinion, the port near the top of the pump won't be high enough to
 be
 > effective for removing air. Just leave it plugged. Better an outlet on top
 of
 > the "water out" fitting that bolts to the top of the pump. The port at the
 > bottom of the water inlet will work for the return line from the heater.
 >
 >Hi, Lynn....thanks so much for taking the time to explain the cooling
 system. When I purchased my custom radiator from C&R Racing, the person I
 spoke to in the engineering section said that I should use this port to send
 water/antifreeze to the side inlet of my expansion tank. He said that I need
 to use a connection point such as this, as there is always water
 circulating, and it is beneath the thermostat.  If I made an inlet higher
 up, which would be above the thermostat, I'm thinking that wouldn't work as
 well?  He said that I could attach a hose to the bottom of my expansion tank
 and connect to the lower hose section where my heater core fluid returns.
 Does this sound correct to you?  Thanks again for your time and
 information.  I guess I haven't totally grasped this yet.  P.S.  The only
 radiator cap I will have is on the top of my expansion tank. I will fill the
 system by removing the upper radiator hose, then fill the expansion tank,
 run the engine, repeat, etc?   Thanks again. Paul Conner

That would be mixing features of two different systems. Both work fine, and
probably mixing some of the elements together would work fine.

The V-8 people tend to run hoses from the back of cylinder heads, and many
other places, to the make up tank. We race in GT-3 and the GT-1 cars are the
astounding TransAm cars with 600 HP V-8s. They have every gag there is working on
the cooling system, but a common theme is the top water bleed idea. To work,
the tank has to be hooked up to the low pressure side of the pump or nothing
will flow toward the tank. That way anyplace that seems to build up steam
because of poor coolant circulation can be scavenged, and the steam pocket problem
is cured. I just reviewed the idea in Carroll Smith's "Prepare to Win."

If you drop back a few feet and look at the top water bleed systems, one
thing stands out to me. The little tank is being used as a swirl pot. In theory,
coolant from higher pressure hot spot areas, is forced into the side of the
lower pressure tank. The tank is kept full to some level, so once in a while, a
burp of steam, or just air bubbles will show up in the tank and pop to the top.
Circulation will continue with coolant leaving the bottom of the tank to
replace the volume of bubbles.  You would want to chase this system, by letting it
cool down and checking water level in the tank a number of heat cycles until
most of the air is removed from the cooling system. I wood keep the tank a bit
over half full to have any system pressure available to drive coolant into
the low pressure side of the pump with speed changes.

The disadvantage of this layout, is that the top water lines must be at the
very top of the tank so as not to entrain additional air in the coolant as it
returns to the tank.
Remember there is constant circulation. I would not vent the radiator to
anything but the tank. Never connect a top water line to the suction side of the
pump. That just puts air back into the engine. The opposite of what you want to
do.

In the diagram, there is a swirl pot. It has only one function, and that is
to collect air bubbles. All of the circulating coolant must pass through it,
and as you can see any such air pops to the top of the swirl pot and is thus
removed from the system. Any temperature changes force the trapped air up the
small ID hose into the bottom of the tank raising the pressure in the tank to
that of whatever cap rating you are running. Only coolant can be recovered when
the pressure changes again. So the tank acts as an accumulator. After a heat
cycle, you will see that the coolant in the tank has been reduced, or is
missing. Refill to half full and run the engine again.
It may take 3 or 4 heat cycles to get the coolant level (always half full) to
stabilize.
After that it never changes.

The rotary has a little problem with holding air in the top of the block. It
has a bigger problem (because of the high mounted pump) with the pump loosing
it's prime. The impeller must be completely submerged. Or, it stops pumping.
Very bad. Any time you have had the system open, be sure to hold you hand on
the water outlet to establish that coolant flow has started.

At the engine speeds that are required, any air will be shoved along at a
high rate  
of speed, and will only collect where there is a space with little flow. Like
the top of a swirl pot. So, I suspect that that it would not be a requirement
to add top water bleeds anywhere. I don't have any, and I just don't have any
heating problems.

Once all of the air is removed, there are no problems.  

I have a Shrader valve in my tank, and I charge the system before I start the
engine. I also have a pressure gage that lets you know when there may be a
problem in the system.

Lynn E. Hanover