Context : The nature of period and amplitude changes in nonradial pulsators is presently unknown .

Aims : It is therefore important to examine the correlations between these changes in stars with a large number of simultaneously excited pulsation modes .
However , the small amplitudes require extensive high-precision photometry covering many years .

Methods : We present 702 nights of high-precision photometry of the evolved \delta Sct variable 4 CVn obtained from 2005 - 2012 with a dedicated telescope .

Results : We detected 64 frequencies , of which 38 can be identified as combinations and harmonics .
The relative amplitudes of the combination frequencies are similar to those found in 44 Tau and show no evidence for resonant mode coupling .
Significant period and amplitude changes are detected for the dominant modes .
The known prograde and retrograde modes show period changes with opposite signs , while the radial mode exhibits only small , cyclical period changes .
For each mode , the period changes are constant over the eight years and range from ( 1/P ) dP/dt = -16 x 10 ^ { -6 } to 13 x 10 ^ { -6 } .
On the other hand , the amplitude variations show no systematic behavior between different pulsation modes .

Conclusions : The behavior of the prograde , axisymmetric , and retrograde modes indicate a constant decrease in the rotational splitting over the eight years .