Let the four consecutive even numbers be \( x, x+2, x+4, x+6 \).
The average of these numbers is 27, so:
\[
\frac{x + (x+2) + (x+4) + (x+6)}{4} = 27
\]
\[
\frac{4x + 12}{4} = 27
\]
\[
4x + 12 = 108
\]
\[
4x = 96
\]
\[
x = 24
\]
Thus, the four consecutive even numbers are 24, 26, 28, and 30. The largest number is 30.