Compute your pulley ratio before you change anything. I chased overheating problems on my '66 for many years....Timing, carb tuning, 3 core, big 4 core ...switched to an aluminum rad, no thermostat, 160 degree, 180 degree, 190 degree, moroso restrictor plates (all 3), new hoses...spring in the lower rad hose, 4 blade, 6 blade fan, 7 blade fan, new fan clutch, shroud no fan clutch, electric fans (2). Turns out my water pump pulley was larger than my crank pulley....effectively underdriving my fan and water pump. I went to the junkyard and asked if they'd point me towards the Pontiac section. After perusing a bunch of engines I found a smaller water pump pulley on a Pontiac engine. After switching the pilley and installing 2 different belts, my overheating problem was solved. The engine now resides in TEXAS in a first gen Firebird. No Problemo!
Divide the crank pulley diameter by the diameter of the waterpump pulley (8" diameter crank pulley and a 6" pulley waterpump pulley gives you a 133% overdriven water pump and fan. I had CVF Racing make an overdrive crank pulley kit. Works great! Check it out, do the math and let us know what you come up with. Hope this helps.
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