My original write-up included details of the impellor deletion from the std OE water pump. If you remove the impellor, you need to block the bypass hole between cavities within the casting to keep the circulation routes isolated. Once the impellor is removed, you also need to bung, or aluminium weld, the resultant hole in the casing. I used a simple rubber bung with a through-bolt to compress-fit the bung within the nose of the water pump housing. This rubber bung set-up has lasted since 2004/5, with only occasional tightening of the through bolt required.
NB. I've chopped a Word document / PowerPoint conversion into jpegs so it's easy to post on here without formatting nightmares. I hope it's all clear enough to be useful.
