Hi all, I have a 540 cube big block in an aussie falcon coupe. My running temp is 190° on the freeway , and 185° on idle. If I give it a bit of a hard time it will go to 195° then straight back down to 190°. This is on a 25°c day, (77°f) . Radiator has been upgraded and have twin 12" thermo fans. Would like to know what temp you guys are running. Bare in mind my motor is pushing a few ponies , 650hp maybe more. I feel 190° is quite normal for a big block. Any input would be greatly appreciated. Cheers
panosxb545
Engine running temp?
👉 Note this response is about expected temperatures, not what they should be for a given purpose.
From a functional and design perspective, the cooling system in healthy condition should provide a fairly narrow range of engine temperatures, from the thermostat rating up to 20-25° higher, under most conditions. For your 180°F thermostat, that would be roughly 180° to 200-205°.
Some short and limited under or over-temp is OK, if under light load. The reason for this target range is wear and tune stability. If we could maintain perfectly stable temperatures, the metals would not change dimensions due to heat variation, and wear would be minimized. The tune would also remain stable if temperatures are stable. Our older-technology systems can't do much better than the range stated, but that's good enough to prevent damage from heat-related causes, and to maintain the tune fairly well.
Just for reference, this is why you've heard that you shouldn't load the engine when cold, nor over-heated. The piston rings are typically the first to be affected, as they now fit differently when over-heated. If temperatures are high enough when loads are applied, the different hot dimensions can literally lose some ring seal permanently. Other damages follow. Trivia - this is known in drag racing as "burning-down", and most rules no longer allow this sneaky trick (delay start) to force the competition out if too hot, for risk of damage.
From a functional and design perspective, the cooling system in healthy condition should provide a fairly narrow range of engine temperatures, from the thermostat rating up to 20-25° higher, under most conditions. For your 180°F thermostat, that would be roughly 180° to 200-205°.
Some short and limited under or over-temp is OK, if under light load. The reason for this target range is wear and tune stability. If we could maintain perfectly stable temperatures, the metals would not change dimensions due to heat variation, and wear would be minimized. The tune would also remain stable if temperatures are stable. Our older-technology systems can't do much better than the range stated, but that's good enough to prevent damage from heat-related causes, and to maintain the tune fairly well.
Just for reference, this is why you've heard that you shouldn't load the engine when cold, nor over-heated. The piston rings are typically the first to be affected, as they now fit differently when over-heated. If temperatures are high enough when loads are applied, the different hot dimensions can literally lose some ring seal permanently. Other damages follow. Trivia - this is known in drag racing as "burning-down", and most rules no longer allow this sneaky trick (delay start) to force the competition out if too hot, for risk of damage.
Good point - I always run a high-flow thermostat for maximum temperature control. I also use a premium version with a jiggle valve, v-notch or other air-purge system. While there are many places you can cut corners without concern, thermostats are not one of them, IMO. Stay cool. 
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