I've got an engine i'm building, and I've had it sitting for a while outside, covered and wrapped in a big plastic bag, but rust still managed to creep into the water jacket. Is there anything I can do about that?

It's a b18c1 btw.

 

Wire pipe brushes. You'll want to get one that isn't much wider than the channel so as not to damage the deck. You may end up buying a set that has the perfect size. Use a softer metal brush than steel. Copper's usually the softest, aluminum and then brass bristles follow. Ideally, you want to use the softest one that will get the job done. Usually stick it in gently where two cylinders meet as there is often more room there. Once you have the brush in, try not to pull it out until you're finished to protect the deck. Thoroughly blow out and then rinse the channels.

 

Ok, thank you very much, is there any certain product I should try using? I'm going to spray wd-40 as much as possible. And get some wire brushes like you suggested.

 

WD-40 is good for cleaning existing rust, but it's not a rust preventative so to speak. there is an industrial product called Ferrocote... but i don't think it's available in household quantities.

i use auto trans fluid as a rust preventative. it works great! thick enough to stay in place and easy enough to clean off later.