That's me!
I used louvers for exit air after the L.O.cooler.
I mounted the louvers (and air exit) on the side of the lower cowl, which is a low pressure area.
Now for the confession:
I'm using an auto conversion; a Mazda rotary. It uses a rather large L.O. cooler. I used the right cowl cheek air supply for this, and exited the heated air out the right side. It works great. Cools on the ground and everything.
My prop is left hand turning. With Lycomings, the oil cooler is usually on the left side, so I would think you would place the louver on the left side of your plane's cowl.
Just consider that air leaving this louver may enter the fresh air supply alittle farther back. You breathe this air, so mount the louver high enough that engine compartment air does not enter the cabin. Although, in your case, this is clean top plenum air, and only passed thru an oil cooler. It's not likely that exhaust products could enter the air stream.
Thorp T-18s use side exit air for the engine cooling, so it's not unusual.
There may be a 'plume drag' penalty. I don't think so, but it's worth telling us about it if you try it.
If you are curious about my cooling; I have a chin scoop for the water radiator, and the left cheek has a diffuser for turbo inlet air, plus surface cooling air for the manifolds.
I have not flown yet, but have 4 hours of ground running time. Cooling is effective in ground running up to 50 indicated H.P. and I can feel the heat coming off the L.O. cooler when I stick my hand out the side into the airstream.
I just move N89SE to the airport.. I'm assembling the wings, control system fuel system wires etc. Then more ground running...Above 50 H.P., where I won't be rude to the neighbors.
Home built engines are not for everyone. Hours of ground testing are required to assure reliable power on the first flight.
Just be glad you have a Lycoming and keep going. (I'm a gear head)
