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Old 01-20-2006, 01:32 PM
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Cooling question

I am running a 355 chev with Edelbrock aluminum heads, an aluminum water pump, a PRC cross flow radiator and a pair of Spal fans set up as pullers. The thermostatic switch is set up to turn the fans on at 195, and shut it down at around 175. With this set up, it takes about 2-3 minutes idling for the temp to drop back to thermostat temp (180). Problem may be my imagination, but on a nippy evening, the temp will bump 200 and come back down. and in traffic it cycles a lot. I think that it is running warmer than it should.
I have drilled a couple of small holes in my thermostat, and have attempted to "burp" the system. It never goes over 200, but I feel that it should not even get near 200 on a 65 night.
Anyone have any suggestions???

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Old 01-20-2006, 09:20 PM
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temp

Temp is fine at those numbers if engine is modified . we run up to 240 in race car some nights on oval track with no problems. if you are running antifreeze replace with water wetter and water ,temp will go lower.Thats of course as long as your not in a freeze area.
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Old 01-21-2006, 12:58 AM
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Keep it cool

Run water wetter and a fan shroud and a good fan on the water pump not one of those cheap 4 blade light weight fans.


Tazz
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Old 01-21-2006, 08:48 AM
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Hi. Process of elimination is the only way your going to find out for sure what's going on. The first thing I'd do is pull the thermostat run without it for a coupla days and see what the temp does. Write stuff down so if you wind up having to check different things you'll be able to keep it all straight. If the temp is the same as before after pulling the thermostat you've either got a capacity problem or an airflow problem. One other thing that I've heard is if the timing is wrong or the carb is lean it can make the motor run hot. With the thermostat out you should be able to do 55 and the temp not go up to 200. Take all this with a grain of salt cause all I can tell ya are things I've tried. One last thing, your sure the fans are pulling air thru the rad? I'm guessing if the wires are reversed the fan runs the other way? Hope this helps.

Moon
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Old 01-21-2006, 09:01 AM
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Quote:
Originally Posted by THADD
I am running a 355 chev with Edelbrock aluminum heads, an aluminum water pump, a PRC cross flow radiator and a pair of Spal fans set up as pullers. The thermostatic switch is set up to turn the fans on at 195, and shut it down at around 175. With this set up, it takes about 2-3 minutes idling for the temp to drop back to thermostat temp (180). Problem may be my imagination, but on a nippy evening, the temp will bump 200 and come back down. and in traffic it cycles a lot. I think that it is running warmer than it should.
I have drilled a couple of small holes in my thermostat, and have attempted to "burp" the system. It never goes over 200, but I feel that it should not even get near 200 on a 65 night.
Anyone have any suggestions???
1. Why wouldn't it cycle in traffic? Cycling means that everything works, it turns on when the temperature goes up, the fan cools the radiator, and the temperature goes down. The fan works well enough to cool the engine to the lower trigger point and it shuts off. What could be better?
2. I would put my thermostatic switch and my indicating sensor very close together, and monitor the operation. They may not operate at the same speed, i.e. the indicator has a rapid response, but the switch has more lag. The difference between 195 and 200 is very slight when you consider the relative accuracy of the sensors and switch.
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Old 01-21-2006, 10:37 AM
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Agreed, it sounds like it's doing exactly what you programmed it to do. Remember that most of the heat energy being produced by the engine is not being converted to work it's waste. Waste heat into the cooling system and exhaust.
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Old 01-23-2006, 07:17 AM
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I have to agree! With a 180 thermostat, temp running up to 200 is perfectly normal, or even as high as 210-215 on a hot day. Water doesn't even start to flow fully until 180, so it's going to get a little hotter as it starts flowing. Some of the dirt track racers remove the thermostat and just use a restrictor plate, sometimes adjustable, but that's no good for a street driven car. The thermostat cycles to keep the engine around 180 degrees, so it will vary from 170-210 or so -- perfectly normal. As someone else pointed out, there could be a lag or just a difference between the sensors also. I just ignore the fan sensor and set my fans by the temp gauge. My temp sensor is adjustable and turns on and off at the same point, and has no temp setting on it. you might want to go with something like that rather than a set sensor, but I'd leave it alone. An engine NEEDS to run at the designed temp for best performance and lowest emissions. I don't know why people want to reduce the temp of the engine, some engineers spent a lot of time figuring running temps out!
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Old 01-25-2006, 04:13 PM
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Are you running a vacuum advance distributor?

Most GM engines overheat without the additional advance of a vacuum advance distributor.

Vacuum advance should be supplied from full time vacuum and not ported vacuum.
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Old 01-25-2006, 04:45 PM
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It looks to me like your system is operating as it should. I do not see any problem with it. My Z-71 daily driver has run 205-210 ever since I bought it new in 99.
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