I finally got the new engine installed and running... but it quickly developed what sounded just like an exhaust leak, coming from the passenger side of the engine compartment. After looking all over and trying to figure it out, I found that the "freeze plug" on the front of the head had popped out.

Now, I didn't look as closely as I should have while rebuilding it, but I had assumed that plug sealed a water passage. Since no water was coming out of it, I'm assuming it actually seals the air injection passages.

Am I right, or is something horribly wrong? I've been watching the temps and coolant usage, and so far, everything looks good, but I'm a tad concerned.

Edit: Head is from a '78 Volare.