Suggestions on cleaning inside of intake manifold

[Musicars]

I'm preparing an engine to replace the one in my '06 Denali. I have the intake manifold off and found the usual oil and gunk inside. Has anyone found a successful method for removing the burnt oil or carbon or whatever it is from the intake runners? Obviously, I can't use metal scrapers on a plastic intake but I have not had much success with chemicals. So far, I have used Gunk engine greaser, brake cleaner, mineral spirits, Simple Green, 409, orange pumice hand cleaner, and probably some things I forgot. I have been using a nylon bottle brush and everytime I flush it the water is light brown so I am removing a little bit but have only gotten it as clean at the attached picture:

 

[Doubeleive]

soak in vinegar? I don't know what oven cleaner might do to it but if it survived all the other stuff...........

 

[Musicars]

I knew I forgot to mention some things I have tried...vinegar and oven cleaner. However, I did not soak very long in the oven cleaner. But I did try both multiple times. I have been considering doing again with a longer soak but have not gotten to it yet.

 

[the_tool_man]

Super Clean in the purple jugs, sold at Walmart. Let it soak overnight.

 

[SnowDrifter]

MEK. In the paint thinners section of your local hardware store


It's rather strong stuff. Trust me when I say you don't want to breathe it

It's safe for the intake plastic, which is glass fiber reinforced nylon. Mind the cleaners you use. Not everything will be safe for it


Another option: soak it in gasoline. It already has some detergents in it for mitigating carbon. ProjectFarm did a video of it where he soaked a gross looking bolt in cheap and nice gas to help gauge the cleaning properties