The debate over using boiled linseed oil on old engine blocks

Last fall, my neighbor Jim swore that coating the inside of my rusty 350 block with boiled linseed oil would stop it from flash rusting. I read a few forum threads that said it just gums up oil passages and traps moisture. I went ahead and tried it on a spare intake manifold first, and after three months in my garage in Nashville, the coated part is still clean while a bare piece I left out is covered in orange rust. But I still wonder if he is right and the internet is wrong. Has anyone else tried this trick on an actual running engine and seen problems down the line?

2 comments

2 Comments

grant_palmer8d ago

Wait, you actually tried it on an intake and left it sit for three months? That's bold. I'd have been too scared to even test it, figured it would turn into some kind of sticky mess.

palmer.henry8d ago

That "sticky mess" line is exactly what I thought too. A buddy of mine tried that carb dip stuff on a boat motor manifold he was cleaning up. He left it in the bucket for maybe two months, not even three. When he pulled it out, the dip had turned this weird thick jelly on the surface. The manifold itself came out clean, but he spent half a day scrubbing that jelly off with a wire brush and some brake cleaner. He said it was like trying to wash off rubber cement that got left in the sun. So yeah, three months is playing with fire in my book.