Very large record sizes and resource usage - Mailing list pgsql-performance

Is there any guidelines to sizing work_mem, shared_bufferes and other
configuration parameters etc., with regards to very large records?  I
have a table that has a bytea column and I am told that some of these
columns contain over 400MB of data.  I am having a problem on several
servers reading and more specifically dumping these records (table)
using pg_dump

Thanks