[dana44]

A small smear of blue RTV silicone or even number 2 RTV. You want to smear it on very thin because when it is bolted down it all squishes out, but a thin layer will seal it without any problem, extra will ooze out, so keeping it out of the internals is important.

 

[ImperialCrown]

What do the gasket instructions say? Silicone RTV may dissolve with gasoline and corrode iron.
If the instructions recommend a gasket sealant, use something like this:

http://www.permatex.com/products/product-categories/gasketing/gasket-sealants/permatex-high-tack-spray-a-gasket-sealant-detail


From the Loctite website for Blue silicone RTV:
http://www.loctiteproducts.com/p/mech_gskt_rtv_b/overview/Loctite-Silicone-RTV-Blue.htm


Not Recommended For

• Not for use on Polyethylene, polypropylene, polytetrafluoroethylene, polymethylmethacrylate, polycarbonate, PVC or Teflon.
• The curing process can cause corrosion to some surfaces. Not for use on brass, copper, magnesium, iron, zinc or galvanized metals.
• Not paintable.
• Use in pure oxygen and/or oxygen rich systems and should not be selected as a sealant for chlorine or other strong oxidizing materials.
• Use on parts in contact with gasoline.

 

[dana44]

And none of these things happen in this application, including the contact with petroleum (gas in this case), because it is not in the ports, it is the mating surfaces, in addition of being tight enough not to allow air leaks or vacuum leaks, or oil seeping through. If you don't like the RTV, use number 2 (brown) Permatex, which I don't think is silicone based.

 

[ImperialCrown]

I have seen problems with carburetted vehicles and Blue RTV. After the engine is shut off, the air/fuel charge left in the intake will seep into the cracks and will soften and dissolve the RTV. Cold and/or flooded engines will soon eventually do the same thing.
The non-hardening Brown RTV is gasoline resistant and may work OK. The hardening Brown RTV may make things difficult to disassemble should the time come. Only use the recommended sealer if told to do so by the instructions.
Again, follow the gasket manufacturers recommendations. If in doubt, contact the manufacturer. There is a lot on the web about this. Be sure that the mating surfaces are dry, smooth and clean.

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=970452&page=1

 

[King Coronet]

Thanks for all the help. The gaskets came in a complete engine set with no special instructions. I think I have a can of that Permatex with a brush (brown color) and will use that.

 

[ImperialCrown]

I would advise you to contact the kit manufacturer by website or 800 number before doing anything. You may void your warranty. Gasket shellac may not be a good idea according to them either. Who made or marketed the gasket set?

 

[chuzz]

I've never rebuilt a 270, but did help my dad overhaul an old 64 318 poly that he had a LONG time ago. IIRC he didn't use any type of sealer on the intake manifold gasket. Just torqued it to spec and in the sequence the Chiltons manual showed. Never had any problems with it.