While everything was easily accessible with the engine out of the car, we decided to block the coolant out of most of the manifold and throttle body to help keep the intake charge air cooler. Since the coolant temperature sensor is located in the manifold, we couldn't block all of the passages. However, we blocked the ones that weren't as critical to engine operation. The hot water heats the manifold and throttle body to prevent icing of the throttle body, and reduces the formation of deposits in both the intake manifold and the throttle body. Once the hot water is stopped, the throttle body will have to be inspected and cleaned periodically.
Ice can also cause the throttle to stick open.
Since we blocked the hot water out of the idle air regulator passage, we anticipated minor idle fluctuations when the engine was cold. The air regulator is controlled by ECU input, with coolant and conducted manifold heat on a bimetallic spring. Since the manifold will now heat up slower, the valve might not function as quickly but we figured that it would be worth experimenting to see if the driveabilty remained acceptable. Because the block had been decked about 0.010-in. When the distance from the cams to the crank is reduced, the difference in chain link distance gets shorter and the cam timing retards.