1986 Dodge D150 318. I'm looking for recommendations and/or experiences using sealant with or without the Power Heat Valve crush gasket. I've looked into the high temp silicone type and the anaerobic flange sealants. I'm leaning towards the silicone based (I assume they are silicone based) if I decide to use a sealant at all.

I'm finally getting around to fixing the exhaust leak off of the right side exhaust manifold. This model/year uses a vacuum operated heat riser valve which mounts to a machined flange on the right exhaust manifold and uses a thin metal crush gasket made from sheet metal. When I installed this salvage yard engine in ~2005 I used a new crush gasket and I guess it lasted reasonably long. It finally rusted out maybe 10 years ago followed by the Air Pump injection line that screws into the right exhaust manifold just above the valve. I got tired of the bark reminding me that the flange surfaces take a hit with every pulse of exhaust gas. There was absolutely nothing left of the crush gasket except some pieces of rust. As you can see from the picture I cleaned up the flange surface on the valve. I used a jitterbug sander with emery cloth and I know it isn't flat, but it wasn't flat when I started either. The mating surface on the right manifold looks better than the valve's surface, but I will have a hard time cleaning it in place which I plan to try first. The long stud next to the block cannot be removed without cutting it or pulling the manifold (or possibly getting the top nut to turn somehow). I have a new crush gasket. I really don't want to have to do this job again due to a premature failure. I also don't want to pull the manifold and bring the 2 pieces to a machine shop if I don't have to. So what are your experiences using the high temp sealants I mentioned?

 

Any variety of sealant likely isn't going to work. Get yourself a sheet of dead-soft copper, or aluminum, 3/16ths, or better, make your own gasket. You will never have to worry about it again.

 

Good idea. Thanks!

 

Replace the manifolds with headers!

 

Haa! There was a time I was going to install a true dual exhaust. I had collected 2 edelbrock manifolds (4brl low rpm torque, and 4brl street) and a new 4brl carb from an earlier year 318 that came with one. Also the motor is a 1987 with the roller cam and improved combustion chamber design. I had dreams but age and injury had different plans. So sad.

I did get the long stud out. I was able to get the small tip of my torch up in there after I dropped the Y-pipe.