To measure the stock intake manifold volume I covered the runner outlets, put fuel injectors in place, covered the throttle body opening, and covered the vacuum port that is located near the throttle body opening. I then used a funnel to fill the intake manifold with water. Once water began running out the vacuum ports at the back of the manifold I stopped filling and emptied the manifold into a larger container. I then measured the quantity of water that was captured.
The water volume would fill 129 cubic inches.
There was some slow leakage from the coverings so the amount recorded is not exact, once the manifold was filled it was almost immediately emptied, so the amount of water lost should not be very great. In addition, there may have been a few drops still inside the manifold.
The point of the exercise was to get an approximate idea of the volume of the intake manifold which was accomplished.