I am replacing my old water outlet/thermostat housing with a chrome version that has an "o-ring" seal. I am not familiar with this type of seal. Is this all I need or do I need to put the usual gasket and permatex sealer on the housing?

If I use just the o-ring, is gasket sealer required also?

And I have a new regular gasket with adhesive on one side. If I use this gasket, do I put permatex sealer on both sides, or just the un-adhesive side?

Thanks for any info.
CB3

 

The engine size is?

 

1978 F-100, 302

 

With O-rings, just use the O-ring, no additional sealer is needed. I'm assuming there's a groove for the O-ring to fit in. You can use a small amount of petroleum jelly in the groove to help keep the O-ring in place while you install the housing.