Good work on using the water manometer to trouble shoot the problem.
You could also try some louvers directly above the back side of the
rads as that is a lower pressure area.  Further aft, just in front of the
windshield, it becomes a high pressure area. Peter Garrison, heavy into
CFD, choose that area for his cowl flaps.

BTW there is an off the shelf low cost (less than $15) product that
is near perfect for this application. It is called a wall vent
with built in damper for central heating system.

Home Depot. Cowl flaps built in. Available in light weight plastic or steel.
They come in many different sizes and styles. Look for the one way versions.

Here is a company with a zillion different products.
http://www.atlantasupply.com/wall-register-vents.htm

Paul Lamar

P,

    Great pressure analysis here...  These things are excellent visual tools...

    In looking at it, the ideal placement for heat exchangers would be
"cheek-mounted" as has already been proven and overstated; however,
the best placement for the "exit" air looks to be just aft of the
"cheeks" in the low-pressure area on either side...!

    This is a far different idea than has previously been presented,
where the exit-air location has traditionally been ventrally placed,
just forward of the firewall -- in a relatively high-pressure area,
I might add.



    Airflow: IN, through openings either side of the nose; and OUT,
through the "cheeks" in the low-pressure area, port and starboard...
I'm thinking either fixed or controllable cowl flaps here...
A pusher-configuration would require a different pressure analysis.

    Your thoughts...?

Jack Beale