I'm with ihscouts on this one. I just did a head gasket job - mine sounded like that til it got even worse. Blew the head gasket out the sparkplug side of the motor. Mine got really bad.





block and head cleaned up fine. Replaced head gaskets (15 hour job but it wasn't bad at all) and it purrs nicely again now.

I initially found the leak by putting one of those telescoping mirrors (mirror on an antenna) down by the exhaust manifold looking around while the engine was running, I could feel air pressure moving it around down there. Took it out expecting it to be fogged up - grabbed the mirror with my hand and just about branded myself it was so hot.

Here are some videos of what mine ended up sounding like before the head gasket job: