Rick,
I'm seeing pegged-out 250 deg spikes! The needle swings to the 250deg mark and then right away starts to drop, only on the first warm-up.. The only thing I can imagine is that there's a recurring pocket of steam that travels past my temp sending unit shortly after start-up. I can actually jump out and feel the coolant part of the intake near the sending unit when it shows 250 deg and it feels fine (no where near what 250 deg should feel like). It's still doing it with 2ea 3/16" holes in my t-sat. I'm going to replace the thermostat (again) and drill the new one with 4ea 1/4" holes this time. I also, as I did before, test it in a pan-o-water on the range w/a thermometer in it. I had the March pullies, actually still have the water pump pulley. I changed the crankshaft March pulley to an OEM larger diameter crank pulley, giving me an overdriven waterpump (overdriven by +0.05%). As I said my cooling capabilities are fine, just that darn temp spike that's driving me nutz!
