LQ9 6.0 exhaust manifold ports - oil burn?

2004 CHEVROLET BEL AIR
5 MILES
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SANCHJU1
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La swap on my 1955 bel air . I followed 2carpros how to rebuilt 5.3 & LS swap vids. I attached three photos - cylinder exhaust port 3 & 7 are black compared to the others. This is from the initial start up. Only stated engine 4 time for no longer than 5mins each time I started it up. There was smoke coming from headers and smelled like rubber. Engine block and heads were sent to machine shop… I’m looking for your opinion please :) . Is this leaking valve steam, position rings? Thank your review and help
Julian .. note sure if photos uploaded please let me know thank you
Feb 27, 2026 at 11:25 AM
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STRAILER
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Hi Julian, I don't see the images can you please try again? Also, the smell is normal on first start up so you should be okay there, it is just the paint on the headers burning a little bit. How does the engine seem to run? Is it misfiring? Can you please upload a short video of the engine running for me? Ken
Feb 28, 2026 at 9:59 AM
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SANCHJU1
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Images uploaded please let me know if you can see them thank you
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Feb 28, 2026 at 10:33 AM
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SANCHJU1
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Quick video
Feb 28, 2026 at 10:34 AM
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STRAILER
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Thanks for the images and video. So it looks like the ports with the carbon are normal, they are rich because the cylinders/spark plugs without color are not firing making the computer think you have a lean condition, so it richens the mixture up. I would start with a compression test on those cylinders (non color), change the coils out, check for fuel injector pulse. Here is a video to help with the compression test.

https://www.youtube.com/watch?v=KOxIm1F8AW0

This guide can help go over the misfire causes and how to check them.

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

Please go over these guides and get back to me. Ken
Mar 1, 2026 at 10:53 AM
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The install looks clean, good job!
Mar 1, 2026 at 10:54 AM