Finnish is not really isochronic at any level. For example, huutelu "shouting" and huuhtelu "flushing" are distinct words, where the initial syllables huu- and huuh- are of different length. Additionally, acoustic measurements show that the first syllable of a word is (physically) longer than other syllables, in addition to its phonemic length (long or short). Thus, there are four distinct phonetic lengths.
Read more about this topic: Finnish Phonology