Im going to add/edit info on the original post. Here’s what I did. I poured 3 gallons of cleaning grade vinegar into a large tub. I wanted enough to submerge the intake. Overnight soak worked pretty well but I wanted to speed things up a bit. So I added some already diluted muriatic acid to the tub. That sped up the process quite a bit. (I’ve used diluted muriatic acid before to wash out a rusty gas tank before sealing it with KBS tank sealer.) Another few hours and the intake was a nice even gray. The second intake only took overnight, so the increased acidity definitely helped speed up the process.
The 30% cleaning vinegar linked above is NOT what I used. I saw it on the shelf but I was not interested in buying 3 gallons at that price. The stuff I bought is less concentrated I’m sure.
Here’s what I would recommend. Safety first! If you feel comfortable handling acid, the get muriatic acid and dilute it 1 part acid to 4 parts water. That should be very effective. Fast results will depend on acid concentration and time. It’s a chemical reaction after all. Some good prep work to get the “tree bark” rust off first will also help.
Never use the acid on an aluminum intake or aluminum parts (which don’t rust anyway)!
Here’s the second intake results. This is a 1958 283ci cast iron intake obtained from Jerry!
