funny looking oil substance from an i/o???

[red20]

My friend was out with us this weekend. He has an open fish w/ i/o power -- small block chevy, holly 4 barrel carb. At idle we noticed a white "milky" substance floating on the surface. It looks like white lithium grease. Must have been coming from the exhaust. I have seen carbon build up / unburned fuel pool up on the surface but never white in color. Any ideas on what this stuff was?