solr search and large dataset


We have an Omeka site with ~32k pdf, full text searchable. solr has started to timeout or throw memory errors when searching for certain words or multiple words, search time is also lagging.

We are using a rackspace vm for the solr server alone, it's on SSD, and has ram to spare. I've tried some simple tweaking by increasing the ram to the java heap, but nothing has really helped.

Can anyone point me in the right direction?

Thanks, Adam