Diode

I just noticed tiny (really tiny) bubbles at the top of the exhaust manifold between cylinders 4 and 6. First I thought it was just oil burning off (slight valve cover leak), but I wiped it down and started the motor again. Sure enough, it's bubbling. Somebody please tell me that it could just be the exhaust manifold gasket, or the manifold just needs to be torqued down. I can't even think about something like a cracked head. Thanks guys.

79corvette

There normally isn't a gasket between the exhaust manifold and heads so I would rule out the gasket as being a problem.

LemansBlue68

Sounds like a leaking exhaust manifold gasket to me. Possibly a cracked exhaust manifold. Try pulling your exhaust manifold on that side. Check out the gasket (if there is one). Take the manifold to a machine shop and they can check it for cracks if it's not immediately obvious. They could also tell you if the face of the manifold is out of flat. If everything's OK use a decent metal embossed exhaust manifold gasket (like FelPro). You might run a compression check just for peace of mind. Look for consistent readings between cylinders.

Generally small block heads will crack near one of the center two exhaust valves often in the thin area between the exhaust valve seat and the intake. That's the hottest part of the cylinder head. However, you'd not likely see it from the outside of the motor. You'd probably notice a loss of compression in those cylinders and your coolant level would keep dropping because of coolant weeping through the crack.

Good Luck!