we use a 15% reduction with serpentine set up
commonly in days gone by 30% was common but I am assuming you are talking about a crate engine and they are typically installed in cars intended for much more power----which means the crate engine has it's tongue hung out most of the time causing elevated temperatures.
spinning the fan a little quicker and moving the water a bit faster tends to help keep them stay cooler
1 to 1 is common when using V belt but 15% has worked fine for us with serpentine
I have a complete KRC serpentine system if you are interested. It comes w/ Stewart aluminum water pump, 4" water pump pulley, 3.5" crank pulley, KRC aluminum power steering pump w/ 4.2" pulley, idler pulley & bracket, all spacers, belt, bolts and hardware. We ran on a 602. I will take $500 for it.
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