Query_cache_size Question

[Mauricio Pellegrini]

Hi, I'm trying to tweak the execution time for querys on my mysql
server which is using InnoDB.

I know that there are a lot of things to check but one of them, perhaps
not the most important, is the query_cache_size.

I have a dual Xeon cpu with 4gb of ram and this is a Linux dedicated
server which runs only Apache and Mysql 4.1.5 

I've declared Query_cache_size = 16M in the my.cnf file 
and I would say that in the whole we have 60% of select querys and a 
40% of update querys.

Is Query_cache_size=16M too conservative considering that I have 4Gb of
ram ?

If so what would be a more efective value?

As I've said before the engine is InnoDB.

Thanks 
Mauricio