Using oversize gets rid of all the inherent restriction fittings suffer from, apart from the actual bend(s). don't forget the 1/2 fittings people normaly use(and scream restriction!) are in fact 9.9mm inner!, far cry from 12mm tube inner, then add that to the bend...
Use 5/8~14mm fittings with 1/2" hose for best fit...
If you can afford it, experiment with the rads, heaytercores are cheap, but bare in mind that PC rads claim to be low pressure drop/unrestrictive nowadays
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Did you read Robotechs graph from the last page?.
http://w3.one.net/~robotech/images/W...ump_curves.jpg
It was a revalation to me
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