My 235/320 has just the opposite problem.  I can't get my oil temp above
200 unless I block about 75% of the NACA inlet.

I have a 1" x 4" NACA inlet on the left side feeding a 6" piece of 3"
dia. scat into the oil cooler which is on the firewall.  The cooler
exhausts directly into the space above the nose gear.  I think the
reason I get such good cooling is that the cowl exhaust area is greater
than normal.  In addition to the slot for the nose strut, there is an
additional outlet of about 5 square inches on each side.  the "engine installation" picture on this web page shows the oil cooler
mounting and inlet.

    http://home.attbi.com/~rbelshe/

Bob Belshe
235/320 500 hrs.