WordPress server load on post

I have 3,129 posts and 4,624 comments with a lot of attachment pages on my wordpress site. I have installed wp-supercache, don’t have many plugins with about 16 queries per page load. I’ve tried optimizing my dedicated server as best I can, but WordPress is still taking it down. I’ve noticed that sometimes when I publish or edit a post, the load skyrockets and won’t go down until I restart httpd.

The thing is the load has been shooting up in the morning when I post, but at night everything is fine even if my site is receiving 4 times as many hits.

Can anyone think of what might be wrong? I’m almost to the point of getting a separate mysql dedi, but I don’t believe I need that kind of setup yet.