Steve in Mesa AZ

I have not encountered exhaust liners before. Your description of their function sounds interesting-- I'll do some reading. The residue was black sooty like a bad fuel burn and not sticky like a bad oil burner. I will pop the rocker arm cover however and take a look at the valve seals. The cover needs a good cleaning anyway. Have not pulled plugs. Thank you again for added information

I will check the manifold for a warp - It did run several thousand miles with a broken bolt in the end of #6. Other than that irritating leak it really ran quite well. Vacuum leaks continually pop up - all the hoses are old and dry. Thanks for the info.

Sorry -- I hope this image is a little more helpful!

I began work this weekend to eliminate the exhaust leak on an 83 280zx. Two broken bolts allowed enough of a leak to be irritating. The engine has 290,000 on it and has never been apart. I bought it from the original owner at 285,000 or so and have only put a few thousand miles on it myself. When I removed the manifolds to replace the gasket and repair the broken fasteners I noted a difference in the color of the exhaust residue in the #4 exhaust port. All the others were a nice evenly burned white but the #4 port was almost completely black(note picture). Has anyone had enough experience with these to know what the difference may indicate? I'm anxious to get it back together and do a compression check. Other than that I am not sure how to proceed. The car has never been altered in any way.