The heat passages are located in the center of the intake manifold/head flange and let exhaust from 1 exhaust port on each head communicate with a cavity under the plenum and pass on to the other head/manifold depending on pressure differential.
The heat passage in the intake manifold center flange will be a raised area,center of the plenum with a manifold bolt on each side of it.
With single exhaust, when the manifold heat valve at 1 exhaust manifold outlet is closed, gases from that bank must pass through the intake manifold to get to the other bank exhaust manifold--unless the pressure can overcome the heat valve spring and open the valve.All this heats the intake manifold/mixture.Not a performance enhancing thing unless you are warming the engine in cold weather for street action.
Last edited by enginenut; 05/27/2012 10:14 PM.
