And if any bolt holes are exposed to a water jacket, you need to seal them with copper coat
In my experience Copper Coat leaks. Not a lot... but it does. CCoat is an anti seize as far as I know. It has some sealing properties, being that it has micro/nano copper that does fill gaps, but holding back scalding hot coolant under pressure for years it will let you down.
Use high temp thread sealant only, again as DoubleTroubleDingo said to be sure to clean threads and chase internal. I ran off looking for my tube, but I think I chucked it... too old half dead with a hole in the tube. I believe it was Permatex. It's a thick white sweet smelling stuff. (I like the smell of all auto chems... including gasoline!)
This is a common mistake sometimes even made by "pro" engine builders. There is an infamous HotRod mag engine build where they use RTV
on head gaskets...!
There are countless iron blocks out there that are weeping... it's a mess... Not the end of the day but why not the right stuff?
Speaking of the right stuff... use the Right Stuff! That black gold. Use it on oil pans, timing covers, valve covers and intake gaskets...
(important!!! ... use sparingly on intake gaskets and I only use on one side, the intake only and leave the head side clean and dry.)
The real deluxe place to use Right Stuff is between block and intake front and rear. I never use the rubber gasket, just Right Stuff.
Dry fit the intake with gaskets to determine how big the gap is and you may need to run a few beads of Right Stuff to build up enough to
contact the intake. And of course if you go hog wild and use too much... it will end up plugging your oil pump intake at the least.
I have a bad habit of not using enough, always at the back of the intake and my new motors end up leaking oil down the bell housing.
And then I swear to make a sailor blush...
