The third line I believe goes under the aux air valve , it heats up an element on the aux air valve to make it work properly. .I believe

Here is a picture of my 76 - 280 it is similar to yours, might help.

If your talking about that big pipe below the head on the block that's for the PCV system. A hose runs from there to the PCV valve screwed in under your intake.

If your talking about that big pipe below the head on the block that's for the PCV system. A hose runs from there to the PCV valve screwed in under your intake. I can't get the pictures in my library to cooperate right now.

OK I got it. Where the red line is.

Edited May 9, 201311 yr by siteunseen

That's the single biggest PCV pipe I have ever seen in my life... Good to know though, thanks!

Yeah, that's good to know. You wouldn't want that flowing coolant.

I wasn't exactly expecting the PCV system to be that damn big, so it threw me off. Thanks!