I drilled three 5/32” holes in the thermostat to keep some flow going through not thinking that would provide any significant cooling, but I guess it does.  First step is to replace the thermostat; then see if it might be appropriate to reduce the airflow into the in-cowl rad – in some way that reduces drag.  But the nice thing is there is no urgency – and my flight regime is not limited.

 

I use a 180 degree thermostat with a single 1/8" hole to allow air to escape. On cold days the engine runs under 180 on yellow laps. That 1/8" hole is enough flow to cool the engine.

 

For best power, 160 degrees on the oil is as high as you need.

 

Lynn E. Hanover