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OK Guys, Here is the straight scoop direct from Lycoming documentation.
The detailed specification for engine model O-320-D1F states "A pressure
relief valve limits pressure drop through the cooler connection to 35 psi.
A thermostatic bypass and pressure relief valve is available as optional
equipment.  It closes at 185 degrees F,  routing all engine oil through the
cooler.  If pressure drop across the oil cooler system exceeds 75 +/- 15 psi
the pressure relief valve opens bypassing the cooler."

In other words, if you have a "thermostatic bypass and pressure relief
valve" installed in your engine, there should be no need for blocking air
flow through your cooler to increase the oil temperature.  If you found that
it was necessary to restrict air flow through the cooler to raise the oil
temperature, then you either do not have a thermo static bypass valve
installed or the one you have is not functioning properly.  For those of you
who want to increase your oil temperature, I suspect that it would be a lot
easier to install or repair the thermostatic bypass valve rather than
building a special flap to restrict air flow.

I believe that the new engines sold by Lancair do have the thermostatic
bypass valves installed.

Bob Jude
N65BJ

LML website:   http://www.olsusa.com/Users/Mkaye/maillist.html
Builders' Bookstore:   http://www.buildersbooks.com/lancair

Please send your photos and drawings to marvkaye@olsusa.com.