The pop can waterblock was a great idea for building a cheap block, but it mixes aluminum and copper, which
will eventually lead to galvanic corrosion and possible failure of the water containment.
You have to give JFettig mad credit for thinking outside the box though.
You'd better serve yourself with a copper cap waterblock like Owenator built. You can search here or on the overclockers.com projects page.
http://www.overclockers.com/topiclist/index31.asp#WATER COOLING ...dozens of projects here.
BTW, don't expect temperature performance on-par with the modern blocks (they're built for cpu's with a much lower wattage of yesteryear)...but it's a nice place to start with a decently easy and cheap to build solution.
My first waterblock (DIY or otherwise) was the PVC cap block built on bunker mentality's website by Tim Whitaker. I believe it was also outlined later on a front page article.
It worked well, and never failed to cool until cpu's began crossing the 60-80 watt threshold.
http://www.overclockers.com/tips111/ ...I replaced the peltier chip with a copper plate.
In the plate I drilled several small holes and soldered in some loops of 12 gage copper wire to add some heat transfer that a simple flat plate lacks.
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