One for those of you with your cylinder head off already and are wondering what you can do whilst you have access.
The stock K-Series head is a pretty poor cast and not very well finished unfortunatley, the VVC heads were much better and even them can do with a bit of a tidy up. Inadequete cooling is usually the root cause of most of our problems, so anything we can do to aid this process is only going to help with the longevity of our engines.
As can be seen in this picture you are meant to have 2 triangular waterways, these can often still be partially blocked with metal causing a restriction in the flow of coolant around the areas where you would want it to be flowing at it quickest.
These are the tools I used, just a small drill piece and used the side of the drill to gradually enlarge the waterways. I could do with getting a small file to finish it off but as of this time I dont have one in my posession.
The results.
The waterway at the ends gets very restricted as its only half the size of all the rest, so in some bad cases flow here can be as little as a quarter of what it is in around other cylinders. Its worth paying particular attention to this waterway.