[CentOS] yum update question and kernel-smp-devel

I have a local yum repository for CentOS4, and from time to time I add 
new (custom) kernel RPMS.

However, when I run 'yum update' on an SMP box, yum 'installs' the new 
kernel, kernel-devel and kernel-smp packages, but 'updates' the 
kernel-smp-devel package.

i.e. I end up with multiple versions of the kernel, kernel-devel and 
kernel-smp packages, but only the latest kernel-smp-devel

What do I need to do to get the kernel-smp-devel RPMS to 'install' 
instead of 'update'?

Thanks

James Pearson