Water or heated air does not "flow through" (from side to side) many intake manifolds - the heat is on transferred through contact at the middle base of many intake manifolds.
That being the case, only one line is needed and, I guess, that coolant-water/exhaust-air are just as good - with exhaust air being (1) safer if it leaks, and (2) quicker with exhaust air providing immediate warming of the base of the intake manifold.
If you have a Clifford/Offenhauser manifold or other manifold that flows from side to side, and the inflow and outflow ports are separated, use a two-port/tube heating plate (and seal it).
gospel1 :
- what type of intake manifold will you be using?
- good luck finding a 2-port "heat plate" (maybe some will post a link)
If you buy from Patrick's, be sure to inform him that you do not want to order unless it is in stock. Use a charge card; and, cancel payment if you do not receive the plate within a week.
