Gary, et al,

 

There are many ways to skin a cat.  I take cabin heatmuff intake air from the lower horizontal baffling aft of the prop flange via a 1.5 in scat tube.  There is no restriction on the air that is dumped into the lower cowl if the cabin heat valve is closed.  This intake location does not alter the cooling air distribution to the cylinders.

 

 Now, let's talk about temperatures. In the colder months, engine cooling is less of a problem because the intake air is cooler and the separate intake for the oil cooler is partially closed to keep the oil temp indication up close to 180.  This is cooling neutral.  Let's also remember that the pressure in the cockpit is much lower than that in the upper cowl.  Thus, there is no problem in getting hot air into the cockpit and I seldom have the heater control fully open when the sun is also helping with keeping the cockpit warm.   

 

In the warmer months, a restriction plate is attached to the intake air opening that changes it from the 1.5" to about .6" and, if the cabin heat valve is closed, that lesser amount of air passes through the muff and is dumped in the lower cowl.  Thus, no super heating of the pipe surrounded by the muff nor will the muff itself radiate high heat in the lower cowl.  This may also allow more of the upper cowl air to be routed over the cylinders to compensate for the warmer cooling air coming in to the upper cowl.  The oil cooler intake air door is open wide and the oil contributes to overall engine cooling.  This is also cooling neutral.

 

Try not to let the unknown unknowns get ya......

 

Hmmmmm....  Never mind.

 

Grayhawk