Silly question, but I am about to put my spark plug tubes back into my refurbished slant 6. There is a new set of tube top seals in my engine gasket set. I was wondering if there is any type of seal where the bottom of the tube seats on the head, or does the proper torquing of the spark plug seal up the bottom?

You need to remove the washer on the plug otherwise you'll tweak the tube which is uncool. They won't leak unless you've already haven't done what I said about the washers. Good Luck

69a100 is correct about removing the spark plug ring washers, as long as you're working on a 1963-'74 cylinder head. 1960-'62 heads, you leave the ring washers on the plugs.

There is no other seal on the tube -- just the O-rings. More detail and links along with tune-up parts and technique suggestions in this post.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Thanks for the tips; I never would have thought to remove the spark plug washers.

The old plugs in the truck when I got it had the washers on them plus a lot of silicone on the tops of the tubes trying to seal them; the old rubber seals were hard as rock.
Does this mean my old tubes likely won’t seal even when I remove the ring?

Probably, You can take the tube and or O-ring to the parts store and get new ones. I got mine a NAPA. Good Luck

No, it just means the previous owner didn't know what he was doing and didn't bother trying to learn. The spark plug tubes will likely seal just fine with new correct O-rings (which you already have).

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一期一会
Too many people who were born on third base actually believe they've hit a triple.