You are completely dead in the water without a heat control valve in the manifold. Some are comfortable with a stuck valve as long as it is stuck in the fully warmed up position. I am not comfortable with that scenario, but is better than nothing, which is what you have.
Chevrolet didn't include a cab heater from the assembly line for these trucks to keep the sale price down. Wouldn't one think that they could have saved money on the sale price by not spending money on a heat valve in the manifold? Must be it is there for a very important purpose, like preventing liquid gasoline from pouring down into the cylinder when the intake is cold, washing away the oil on the cylinders, creating premature engine wear.
In the case of the OP's scenario, heat is being applied to the intake manifold all of the time. That is not good either. It is likely the cause of the overheating issue.
Last edited by 52Carl; 09/20/2022 1:47 AM.
