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A new flange inlet tube (number 2 in the photo) need to be inserted into the engine block's bore (cast iron). Is it okay to apply a thin layer of silicone grease (against rust) on the walls of the bore before inserting the metal tube?

1 Answer 1


There is no problem with lubricating the tube prior to insertion. It will not create any issues for you.

Something to consider is, what are you actually sealing against? If you are trying to contain any kind of liquid such as oil or water, you might want to consider using a sealant. It will lubricate it during insertion (help smooth the way), will seal the part and block against corrosion, plus it will contain any liquids you might be trying to keep in the block (oil or coolant). Might be a better choice than just silicone grease.

  • May you mention an example of a sealant that may use for this purpose?
    – xchcui
    Nov 23, 2022 at 15:27
  • 2
    I like to use Permatex The Right Stuff. It seals just about everything and anything (oil or water), and usually gets it done the first time. It is a bit more expensive than other sealants, but in my book, well worth the cost. Nov 23, 2022 at 16:01
  • So,you mean i may apply the sealant the same way as i meant to apply the silicone grease?Thin layer all around the bore's walls?
    – xchcui
    Nov 23, 2022 at 16:47
  • 4
    I'd put it on the part instead of the bore, but yes. If you put it in the bore, it will squish it down and could possibly go down into the block. If you put it on the part, it will squish up and seal around the outside edge. Nov 23, 2022 at 17:53
  • 1
    @xchcui - It will cure just fine. I have NEVER had an issue with The Right Stuff curing or sealing, which is why I mentioned it. (NOTE: I have no affiliation with Permatex.) Nov 26, 2022 at 12:39

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