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Old 09-13-2006, 06:16 AM
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Overheating issue when under load?

I have a mopar 440 stroked to 493, alum heads, holley 850 DP, TTI headers, mopar electronic ignition, alum rad with twin 12" spal fans/w shroud and a seperate trans cooler. The problem I am having is this engine wants to run warm when I put it under load. For example, while cruising at about 60 mph it runs about 190* and when I come to a hill and need more throttle the temp will climb to about 205* and when I let out of it and return to normal cruising with minimal throttle she will cool back down a little. This is a new rebuild that only has about 100 miles on it. My timing is set at 36* total and I don't use my vacuum advance. I tried retarding it all the way down to 12* initial and it had no affect on the temp except the motor didn't like 12*. Does this sound like a lean condition? Any advice/help is appreciated.

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Old 09-13-2006, 07:10 AM
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Not enough fan or not enough radiator would be my guess. Also you may want to check to be sure the hoses are not collapsing. I would have the radiator checked, could be plugged or just plain to small for the increased horsepower.
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Old 09-13-2006, 08:08 AM
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Quote:
Originally Posted by Steves66
I have a mopar 440 stroked to 493, alum heads, holley 850 DP, TTI headers, mopar electronic ignition, alum rad with twin 12" spal fans/w shroud and a seperate trans cooler. The problem I am having is this engine wants to run warm when I put it under load. For example, while cruising at about 60 mph it runs about 190* and when I come to a hill and need more throttle the temp will climb to about 205* and when I let out of it and return to normal cruising with minimal throttle she will cool back down a little. This is a new rebuild that only has about 100 miles on it. My timing is set at 36* total and I don't use my vacuum advance. I tried retarding it all the way down to 12* initial and it had no affect on the temp except the motor didn't like 12*. Does this sound like a lean condition? Any advice/help is appreciated.
This actually sounds very normal and expected to me. 205 degrees is not hot using todays options. Higher pressure radiator caps (16#) and higher temperature thermostats (195 degree).

When going up a hill (long steep ones are the best to show the conditions you described); an increase to the accelerator pedal will cause a vacuum drop and a temporary lean condition. The vacuum drop will also cause a slight retarding of the timing (if the vacuum advance is hooked up...not your case though). Both the retarding of the ignition and the slightly lean condition will result in higher temps in the engine and a resulting increase in the coolant temps. The temps should return to 'normal' once back on a more level surface and the vacuum returns to 'normal' cruise level.
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Old 09-13-2006, 08:14 AM
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Thanks T-bucket. The alum rad is new, so it shouldn't be clogged, but it could be too small. It is 28X20 2 core. How could I tell if the bottom hose is collapsing? I made a spring out of a coat hanger wire and put in the bottom hose to try and prevent it from collapsing. As far as the fans, how much cooling do they do while cruising? Seems like I have read somewhere that at highway speeds the cooling system relies on the air coming in from the grill.
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Old 09-13-2006, 08:18 AM
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Frisco, this makes perfect sense because my plugs don't show any signs of being too lean and they wouldn't if I only have a temp lean condition from not having my vacuum advance hooked up. And yes the temp does drop back down to normal when I am on flat ground.
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Old 09-13-2006, 08:42 AM
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Look at it from a physics standpoint.

You are cruising down the road making 'x' horsepower at your cruising rpm and the engine heat balance point is 190. You come to a hill and increase the power to 'x+' yet the engine rpm remains the same. This means that the water and air flow through the radiator remain the same but you are trying to exchange more heat. Your engine temperature will increase until the radiator efficiency becomes high enough to balance the heat generated in the motor.
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Old 09-13-2006, 10:41 AM
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Quote:
Originally Posted by onovakind67
Look at it from a physics standpoint.

You are cruising down the road making 'x' horsepower at your cruising rpm and the engine heat balance point is 190. You come to a hill and increase the power to 'x+' yet the engine rpm remains the same. This means that the water and air flow through the radiator remain the same but you are trying to exchange more heat. Your engine temperature will increase until the radiator efficiency becomes high enough to balance the heat generated in the motor.
I have a Gear Vendors Overdrive, so while I am cruising at about 2000 rpms and I approach a hill and start increasing throttle the rpms will increase to about 2400 without affecting speed. I am really at a loss with this one. I have read so many good review on an alum rad and electric fans that pull 2800 cfm.
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Old 09-13-2006, 11:20 AM
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Quote:
Originally Posted by Steves66
I have a Gear Vendors Overdrive, so while I am cruising at about 2000 rpms and I approach a hill and start increasing throttle the rpms will increase to about 2400 without affecting speed. I am really at a loss with this one. I have read so many good review on an alum rad and electric fans that pull 2800 cfm.
There's nothing to be at a loss about, more power made in the engine requires more efficiency in the radiator to get the heat out. The efficiency of the radiator is directly controlled by the difference between the radiator temperature and the air temperature. In order to get the extra heat out of the engine you have to raise the radiator temperature. If your thermostat is unable to compensate by increasinng the flow, the cooling system will compensate by increasing its temperature until the heat exchange is balanced.
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Old 09-13-2006, 01:42 PM
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Quote:
Originally Posted by onovakind67
There's nothing to be at a loss about, more power made in the engine requires more efficiency in the radiator to get the heat out. The efficiency of the radiator is directly controlled by the difference between the radiator temperature and the air temperature. In order to get the extra heat out of the engine you have to raise the radiator temperature. If your thermostat is unable to compensate by increasinng the flow, the cooling system will compensate by increasing its temperature until the heat exchange is balanced.
I think you misunderstood what I am at a loss about. What I am at a loss about is the hype of the alum rad. The particular rad that I bought is advertised to beneficial for use in racing/high hp applications.
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Old 09-13-2006, 02:15 PM
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I would hook up the vacuum advance and get some more advance at your cruising rpm because I'll bet your mechanical curve isn't halfway engaged at 2000 rpm. Do you use a high volume water pump driven above engine speed?
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Old 09-13-2006, 02:40 PM
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Quote:
Originally Posted by Steves66
I think you misunderstood what I am at a loss about. What I am at a loss about is the hype of the alum rad. The particular rad that I bought is advertised to beneficial for use in racing/high hp applications.
Aluminum radiators do dissipate heat better than copper ones, however it still needs to be sized large enough and have enough air moving through it to remove the heat. You could also try a better thermostat. The average off the shelf is only accurate to +-10 or so. So if you are running a 195 it is possible to get the water to 205-210 before it opens.
the other think is to make sure your grill is not restricing air flow and that all the original air dam crap that is underneath a lot of the newer vehicles is still in place. A radiator is usless without airflow.
lastly 205 is not unreasonable at all and well within what would usually be concidered normal operating temperature.
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Old 09-13-2006, 03:55 PM
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I have a BeCool in the 59--for the 59.
Thought I had a rough time with temps 'til I got the timing and fuel figured out.
I have just over 850 miles on the 454 Crate/Tremec TKO and it seems to me that is is starting to run cooler all the time.

Last few times it was out I did not even get to 190, and only crept to 200 after a grade and pulling into my garage (i have 2 hills to climb before I get home)

I am still running a 160 t-stat. I will probably go to a 180 soon.

Your's just might calm down after a few miles.

Bryan
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Old 09-13-2006, 04:07 PM
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I guess that running 190* you are on the thermostat (180*). If you are running a 160* thermostat then 190* is showing you that your cooling system is insufficient for the ambient temperature in those conditions.

Fans are useless above 35 mph.
Factory type shrouds can actually enhance the air flow by their venturi action. Fan clutch type fans and factory shrouds are recommended.
Water pumps should be overdriven.
205 is not a problem. 230 is borderline with consistent water flow.

Air dams and flow directors might be needed. Air does not always go the direction it looks like it should go. Get the air in and OUT of the engine compartment.

Seal the lower core support to the bumper, the upper core support to the hood, and plug all the holes around the radiator. Make all that air go through the core.

visit www.readershotrods.com
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Old 09-13-2006, 05:06 PM
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This may actually settle down a little once you get some miles on the engine. Once it loostens up a little there will be less friction to generate heat.
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Old 09-14-2006, 03:14 AM
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Thanks for all the advice fellas. My hopes are that it will calm down some, but in the mean time I am going to try all the necessary things I can to try and help cool it down a little. My thermostat is a Mr. Gasket 160* and I do use a alum high volume water pump driven by the stock pulleys. I just put on a new hood to rad support seal, but I don't have the lower seal to bumper in place. I will install that, and plug up any other holes I find and hook the vaccuum advance back up to see if it helps any. Although temps are getting cooler outside so I may have to wait till next summer to get accurate temp readings. Once again, thanks for all the help and any other advice is surely welcomed.
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