Background: First of all I live in Phoenix…cold is below 50 and I rarely drive in the cold. I had to remove the upper cylinder tins to grind a channel for cylinder head temp sensors so the area is already opened up. I don't have a thermostat or cooling flappers and I have an external cooler with 180F thermostat and 212F fan switch mounted under the rear trunk. My oil temp runs around 220F, sometimes a little warmer during prolonged high speed freeway driving.

Should I leave the oil cooler side flapper off like it is; or install a flapper and fix it in the open position to route some cooling air thru the cooler?

Thanks

Removing the flappers is an all around bad idea.

You already answered your own question, the passenger side flapper should be installed and in the "down" position (default mode if the thermostat is removed or failed) to give full air flow over the stock oil cooler.

If that flap is missing completely, you don't get any air flow over the cooler. Bad idea.

Did you get a picture of where you ground?

I want to do the same. I was also considering making a removable panel for easy access. Since mine a a racecar, I would need to pull the plugs more frequently than a street car, so it needs to be relatively easy.

Thanks Andy - I'll install the passenger side flapper
Stu - I'll post a before and after pic after the grinding is done; later this week.