I don't ever use RTV on gasket surfaces on B20s, but I am dealing with a stubborn intake / exhaust gasket on my daily driver. I'm on the second gasket, and cannot get the intake to seal. Both surfaces are clean and the intake was trued up by a reputable machine shop. Have the correct washers, the intake / exhaust surfaces where the washers go are even. Nuts were all torqued evenly to 18 ft-lbs. Even tried up to 25 ft-lbs. I suspect the gasket material is a different composition than that used many years ago and just does not squish like days of old.

At any rate, since I cannot get the gasket to seal I'm going to (begrudgingly) use RTV. I was going to use Permatex Black, but the Permatex Copper says it's more flexible - little confusing. I think the Copper may be the way to go.

I know this has been covered many times, but since I never used RTV in the past, I usually didn't pay attention to others suggestions...shame on me! So now it's my turn. Any thoughts on the Black vs. Copper? (I think the Blue will not stand up to the temperatures of the exhaust manifold.)

Thanks.
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'60 PV544, '68 220, '70 145, '86 745T