273 exhaust manifold bolts. Sealant or no?

Back again folks!
I noticed on my 1964 273ci that the exhaust manifold bolt thread bores aren't sealed from the water jackets in the heads. I used some Permatex silicone on them but I'm thinking it's too hot for that stuff.
I'm also wondering what the connical washers on the exhaust bolts are for. Maybe to prevent the bolts from snapping because of hot/cold cycles?
Thanks for any help.
Author: admin