Can someone tell me what this port is for?

Curious, that is where I put my oil temperature probe. Now the question: what is the port you installed the temp sensor in? I will go look in my Lyc materials.

Common error. That's the oil temp probe port in the top of the filter adapter. Here someone has installed the oil temp probe in the top of the passage coming up from the pump. That would indicate sump temperature or close to it when the vernatherm passage is open. It won't have any flow when the vernatherm passage is closed, so I don't what you would get.

The correct temp sender port is under the red plastic cap. It is assumed to measure temperature of the mixed flow from the oil cooler and vernatherm bypass port.

The port in the background is simply capped off. There should be no viscosity valve piston and spring installed under it if a vernatherm is installed.

It should be a plug (preferred) or a plunger.

This thread gives lots of detailed info -

http://www.vansairforce.com/community/showthread.php?t=45548

Thank you

Thanks guys, I put the temp sensor in wrong port, will reinstall plug and put where the red cap is.