Well I think I just found my problem.. Head Gasket!

Took a quick drive to warm it up, let it idle a bit. While it was idling I was poking around under the hood and noticed my cooolant overflow jug was empty. I filled it up with the engine running and noticed bubbles coming from the overflow hose.

When you rev it up, the bubbles increase. I verified this by putting the hose in a jug full of water. The fumes coming off it smells like exhaust.

Now I'm thinking after turning it off, the pressure in the cooling system bleeds off into one of the cylinders..

Are the coolant and exhaust passages in the head near each other on this motor?

 

Sounds like you found the problem. You could do compression and leak down tests to verify (see compression test link in my signature).