Packard Forum Index » Post-War (1946-54)

Which sealant should I use? I was thinking of using Permatex 27039. It is good up to 750 degrees and has a 2 hour working time. It does say "Note: Not recommended for head gaskets or parts in contact with gasoline." Probably minimal contact with gasoline on the intake side.


permatex.com/products/gasketing/red-gask ... red-rtv-silicone-gasket-maker-3-oz/

No sealer is used or needed on Packard manifold gaskets as long as you’re using a proper gasket.

I will be using a manifold/block gasket sealant. The manual also says no intake/exhaust manifold joint gasket is needed. I will be using an intake/exhaust manifold joint gasket, with sealant.

Amateur enthusiast here, but having done the intake/exhaust manifold gasket a couple of times, I've been curious about this added "insurance" as well. For me, I would probably be inclined to just use the copper spray sealant you would use on a head gasket. I probably wouldn't use RTV, mostly because of the heat cycling your manifold will experience. The manifold needs to be able to "slide" on the gasket. I would think RTV wouldnt permit sufficient expansion without cracking, or just ripping the gasket apart. The manifolds really move A LOT.

I was curious what other flathead communities talk about on this subject, and it's all sort of consistent - make sure both the intake/exhaust manifolds are flat, and same for the block. From there, torque to spec over several passes from the center out. I would say, too, that if you've had manifold surface machined, file the edges to round them off. The sharp edges left after machining will ruin the gasket quickly through heat cycling. Beyond that, most say clean and dry, with some mentions for the copper spray.

Other considerations: You may want to look for an OE-style gasket (they're a little different than the set you would get from Olson's), use brass nuts, and plan to re-torque periodically after heat cycling.