[buwalda]

PopsGTO [ July 1 post ],
I also have a 66 GTO & it ALSO overheated on the highway. I'll bet you are using a clutch fan, because that is what made my GTO run hot on the highway. I tried a few different fan/clutch combinations & they ALL ran hot. I switched to the Pontiac Ram Air 7 blade flex fan & that reduced the highway temps. Also tried a Flex a lite flex fan & it too reduced the temp. I believe the clutch fan free wheels at highway speeds & acts like a baffle, causing temp to rise. Also, clutch=slippage=less rpm turned by fan.


To George K's question about stamped v cast impeller results,

There seem to be many variables that can affect results [ better or worse ]: T'stat rating, T'stat design [ standard, high flow, opening area ], ignition timing, jetting, scale in coolant jackets, under or overdriven water pump pulley, fan-to-radiator distance, shroud/no shroud, radiator condition, small coolant passages blocked in head gaskets?, matching hole in water xover opened to same size as head core hole [ E'brock manifolds have terrible mismatch here ], etc