I put a link to an image below. Hopefully it works for you; it did for me.
On my 68 OHC 6 exhaust manifold is...well something. It's outward appearance is that of a lever. It seems to operate a butterfly valve inside the manifold. I can freely rotate this thing clockwise from its resting 9:00 position to straight up 12:00. The shaft for this valve goes clear through the manifold and protrudes out the other side. There is nothing attached to it. I can feel it rotate with the 'lever'.
I can't find anything in the 68 manual. In the 67 manual I found a reference to a heat control valve. It had a thermal spring attached to it (on the block side). I don't have this spring.
So I kinda sorta think I know what this thing is. I read and understand what a heat control valve does. (It redirects warm exhaust air into the intake for cold startups...something like that.) If I'm anywhere close to right then mine ain't working. Fine. The engine seems to work fine. But I have an unanswered question; is the resting 9:00 position directing the exhaust into the intake or out the tail pipe? I'm baffled.
