i bought aused upper and lower intake manifold for my 302 5.0 mustang engine.
my question is how to i clean the inside of upper intake manifold.
it has this thick black dried oil residue all in it. I tried degreaser and a tooth brush but it doesnt clean it very well and plus i can only go so far.
i want to clean the whole inside if possible because it dont want any of that stuff falling into my new rebuild engine.
i thought about gas but id rather go a diffetent route.

ANY SUGGESTIONS ???