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overheating at what rpm?

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overheating at what rpm?

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Old 10-10-2011, 11:24 PM
  #1  
bradleyb
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I have a 66 mustang coupe with a 302 engine and C4 transmission with 4.25 gears in an 8" ford rear end. I also have a Vintage Frontrunner serpentine system with a 2400 CFM electric psyclone fan from Jegs with a Northern aluminum radiator, 160 degree thermostat with a 194 degree fan switch. When driving around town, the car never gets over 180-185 but when i go on the freeway, it will heat up to around 205 after 10 minutes or so (live close to the on ramp). When driving on the freeway, the RPM with the low gears puts me at 3400 rpm at 65 mph.

The guy at the cooling place told me that the RPM is too high and that is causing some of my cooling issue - even though the guy told me that 205 is not dangerous to the engine (he said that until I get over 220 or so, there shouldn't be any damage to the engine). The guy told me that my engine could have some blocked cooling passages or perhaps my RPM was too high (they flushed my engine/radiator twice and I have a gano filter that is running clean),

What does everyone think - is this 20 degree increase in temperature due to the high RPM? i think that the cooling system pieces are working correctly - I drove for an hour on the city streets and didn't overheat. I read somewhere that the redline for the 302 engine can be as low as 4400 RPM .
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Old 10-11-2011, 04:53 AM
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kalli
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a) that thermostat is way too low. use 190 or so, not 160, and for this maybe the fan switch is on the low side as well. is the fan the right orientation? not that it actually blows the wrong way around???
b) 205 should be still ok
c) 4.25:1 gearing in the back explains that high rpm. doesn't surprise me

very hard to tell what's normal, what's not. however 3400rpm on long duration should be ok for a such an engine. we're not talking 5000 here.
What could be a factor as well is things like:
- ignition timing, retarded timing causes engine heat
- pulleys at waterpump and crank not the right dimension (can cause the waterpump and fan to run too fast/too slow)
- in my experience heating on freeway means too small radiator. But is your car actually overheating? I'm not too sure ....
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Old 10-11-2011, 03:00 PM
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jlg2002
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This just happened to my son's friend, I advised him to change the thermostat and he found a bunch of crap clogging his present thermostat preventing it from opening fully. it's worth a look.
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Old 10-11-2011, 04:42 PM
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Gun Jam
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Originally Posted by bradleyb View Post
I have a 66 mustang coupe with a 302 engine and C4 transmission with 4.25 gears in an 8" ford rear end.
That must suck unless all you care about is your 0-60 time then its great... but if you are actually driving your car now would be a good time to suggest a t5 upgrade Get a cobra or z spec t5 with a .63 OD you could drive the car on the freeway no problem then how does 80 MPH at 2800 RPM sound??

1) Yes switch to a 190 or 195 Tstat
2) 205 is normal operating temp
3) suspect that a 195 tstat will get you back around 200F
4) Time for a t5!
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Old 10-11-2011, 04:56 PM
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1slow67
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This thread actually helped me too. I have been running hot occasionally, so when I saw this thread I went and looked up what thermostat I bought. And what do you know, 160 degree.
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Old 10-11-2011, 07:54 PM
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hahaha just felt like it was time for a change
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Old 10-12-2011, 08:34 AM
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JMD
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IMO the high RPM has little to nothing to do with your temps.

I know it is a dumb thing to bring up, a customer brought in a truck with overheating problems on the highway, the fan was WRONG and trying to push the air through the radiator the wrong way (against the vehicle motion)....


But back on track, I would take the car on a longer ride down the fwy to see if the temp climbs past 205, if it doesn't, I wouldn't even worry about it...
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Old 10-12-2011, 12:21 PM
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crunchyskippy
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Originally Posted by Gun Jam View Post
That must suck unless all you care about is your 0-60 time then its great...
I'm not sure about the BradleyB, but that statement fits me pretty well. I'm actually trying to decide between 3.55 and 3.80 to go with my C4. I rarely drive on the highway, so extended RPM's are not an issue. I'd love to upgrade to a T5 but I've got a long list ahead of that.
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Old 10-12-2011, 12:37 PM
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well if you plan to go with the t5 someday get the 3.80s they will be a little much for the c4 but come t5 time you'll be like a pig in clover.
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