Hi,
delay in EIGRP metric calculations is not a dynamic value; the default delay value of an interface should reflect typical (average) serialization delay values for the particular interface-type.
It is a static interface parameter, and its (interface-type-dependant) default-value can be changed by the delay command, similar to the bandwidth command. To calculate the metric to a destination, EIGRP uses the lowest bandwidth of all interfaces in the path but the sum of all the delays (minimum bandwidth but total delay).
HTH
Rolf