Oil Foaming

Sam Purpura wrote:

What is the oil level in the tank? If the oil level is higher than it likes the excess is blowing out the vent line. I know on my 914 and 912 uls they like to be at the lower end of the dipstick.

Also low end of the dipstick for me anything above 1/4 of the lower limit line and it just blows right out of the overflow / bypass

Foaming Oil is usually a symptom of contamination or excessive ring blowby.
Before doing a compression test; Do a ground run starting with a cold engine.
Tye it down and start it up.
As soon as the Oil reaches the Operating range (125°F), throttle up to ~4000 rpm and leave it there.
Have someone safely watch the Oil Vent tube to see when the Oil Blowing starts.
If it starts right away, defer to the Compression test.
If it doesn't start until it gets a bit hotter, Suspect trace Fuel or excessive Water in the Oil.
Water will not start to boil until well over 200°F, but gasoline may start foaming at 140°F.

Pretend that you are airborne and do not see what is happening back there and let it keep blowing.
You should boil off all the Gasoline before reaching 200°F and the water will be gone by 220°F.
If it keeps blowing above 220°F, Defer to the compression test.

Consider sending an Oil Sample for comprehensive testing.