People have reported leaking at these plugs. I do not know how they sealed the leaks (high heat JB Weld?).
I have used both coolant and exhaust gas with your same set-up.
I prefer to use the correct 2-pipe-hole intake-base-plate that seals through the middle of the plate (with either coolant or exhaust gas/heat). The single pipe/hose plate does not take advantage of the end-to-end (in-and-out) flow that the Offenhuser instake provides.
I have used both coolant and exhaust gas.
I prefer exhaust gas because it heats up the intake more quickly than the coolant does.
I prefer exhaust gas, because the coolant "allows a disaster" if/when a hose breaks/leaks.
