Looking for some ideas to remove rust patches from inside my header tubes. These headers are ceramic coated outside so I don't want to damage that coating.

I have same issue, I broke down and bought a stainless kit and collectors and having them fabricated. The only thing I could think would be any good is to protect the outside and sandblast inside as far as possible. There may be a better approach.

Huh? You guys have way too much time on your hands. LOL.

Have the inside coated....??

Take headers off and go buy a bristle brush for cleaning furnace and use that

Or small diameter chain in a drill

I bought a 2” stainless round brush kit off Slamazon. Has an eye on one side so I’m hoping to pull it through a couple of times. I’ll let you know in a day or so .

Buddy Chuck also showed me a bag of old small nuts and bolts emptied into tubes, tape off and shake it all directions . Worked well!

Arent they just going to rust again as soon as motor is fired up and moisture accumulates? Its why you see water dripping out of any cars exhaust after startup. Not to mention when motor is not running the ambient moist air gets in there and rusts bare metal.

Only way to really prevent it is to coat the inside.

Mine are on year 10 here is **** weather PA and have not rusted thru. They were junk hedman ones to start with painted with rattle can ceramic heat paint. So I would imagine you have 20years on a good set.

Get some heat paint and 3d print a flexible nozzle to pull back thru each primary while spraying the ceramic. Mine have zero rust on the outside and look like new painting them with the heat paint. Look ceramic coated.