8. (10 points) As shown in the figure, a large cube with an edge length of 4 is formed by 64 smaller cubes with an edge length of 1. Then, 4 smaller cubes (the shaded part in the figure) are removed from top to bottom. If the inner and outer surfaces of the remaining solid are painted red, how many smaller cubes have exactly two faces painted red? $\qquad$
【Analysis】First, analyze the small blocks on the edges. Apart from the hollow channel, there are no others on the faces. The numbers in the hollow channel can be added up.

【Solution】Solution: According to the problem:
On the edges of the large cube, there are 6 on the top and bottom each, and 8 on the side edges, making a total of 20 on the edges.
The hollow channel produces 2 on the top and bottom each, and 4 inside the channel, making a total of 8.
In total, $20+8=28$ (blocks).
Therefore, the answer is: 28.