Apparently, the manufacturer and vendors give no serious consideration regarding selling the Offenhauser intakes with leaking plugs - "let the buyer beware".
Tom Langdon will suggest water heat, which the Offenhauser intake allows to circulate from end-to-end of the intake (most other dual intakes do not allow this flow from end to end). It works very nicely, as long as the plugs are sealed.
I have also used heat transfer from copper tubes between the headers and the intake. It works very nicely and I do not need to worry about water leaks or coolant-hose breaks. I prefer two copper tubes because, my simple mind likes the symmetrical appearance.
As posted above, the exhaust-heat method provides heat immediately, but the water-heat cannot supply heat until the coolant heats up.
The pros/cons of water-heat, exhaust-heat, and the one vs two copper tube can be argued, but that will not resolve which technique is better - do what you like.
Does anyone know if JB-Weld will hold up to the heat transferred when the exhaust-heat method is used? My Offenhauser did not need to have the plugs sealed (it did not leak coolant or exhaust gases - I used both methods), so I do not have first-hand experience.
