wyomingoutlaw said:
I built my lemans for the strip, but it still sees an occasional cruise around town. the problem is while cruising around town the temperature slowly climbs to around 210 where I get nervous and shut it down. my temperature sensor is in the intake water crossover, which would be the hottest point, but that still seems mighty warm. I'm running one large electric fan, as I've never had a problem before with electric fans keeping an engine cool. I'm not running a thermostat, but after describing my problem to a fellow hot rodder he told me that is my problem. that seems wrong to me; wouldn't a thermostat restrict the coolant even when it was fully open? or am I missing something? I would just toss one in and try it but my intake sits on top the water cross over making it a bit of a job. what do you all think? are any of you running thermostats in your strip cars?
Assuming the gauge is accurate there are two common overheating events, one is hold temp at cruise and get hot at idle, two is stays within bounds at idle and gets progressively hotter at cruise.
Taking "one" first, this is almost always the result of insufficient airflow across the radiator.
- We've had people using electric fans that were wired backwards blowing out the front that experience heating at cruise and not at idle. If you get pump driven fans cross pollinated between factory V-Belt drive and Serpentine drive, you'll have the same condition as factory style Serpentine
drives turn the reverse direction from V-Belts.
The second one is stickier because there's lots of causes, but in simplicity it's not enough coolant flow getting thru the radiator.
- The same drive issues as above but applied to water pump selection.
- If your running a thermostat, the engine, especially SBCs want a bypass, this allows passage of trapped vapor and eliminates pump and cooling jacket flow separations and cavitation. You can get around this by drilling a couple/ three 1/8th or 3/16th holes in the thermostat, but this adds warm up time.
- The thermostat is there to have control of engine temperature by providing an obstruction to flow to what ever degree is necessary to maintain a proper operating temperature. Wear, pollution, power, fuel economy all suffer when the engine is insufficiently warm. Racers do away with thermostats as a reliability issue and replace them with a washer type restriction. This is only done to remove a simple but show stopping failure point, no more rocket science than that. But racing an engine at WOT for laps on end is a way different problem than driving on the street in all kinds of weather. Contrary to what a lot of racers believe, the most power an engine develops is when it is hot around 200-220 degrees and is inducting cold air, not when the engine is cold. There are so many "rocket science" studies on this for well over half a century that I find it incomprehensible that this idea persists, but it does.
- Insufficient flow the the radiator is caused by:
- Radiator simply too small for the task
- Radiator plugged with corrosion by-products. The cooling system is a
battery where dissimilar metals are exchanging electrons thru the
coolant which acts as an electrolyte. Distilled water and a proper mix
of "coolant" with semi-annual changes will minimize this. The engine,
also, carefully needs to be grounded to the frame to minimize voltage
potentials with in it.
- The use of insufficiently sized electric pumps or the use of underdrive
pulleys. A V8 needs about 10 gallons per thousand RPMs of coolant
circulation.
Other effects especially with custom installations can be a lack of air flow thru the engine compartment especially where air conditioning heat exchangers are ahead of the radiator and or the engine compartment is small and crowded preventing good air movement.
Some fixes for this can be the use of separate transmission and engine oil coolers to take some BTU load off the cooling system. Insulating headers and exhaust systems under the hood. Hood louvers or shimming the hinge if rear mounted to provide an escape route for trapped air. The latter reduces under hood air pressure allowing better fair flow thru the radiator.
Bogie