250 wATER TEMP QUESTION - The 1947 - Present Chevrolet & GMC Truck Message Board Network

NicoSlam · 10-17-2010, 07:55 PM

I installed my old 250 in another truck that had auto meter gauges. I got it running just as it did in my truck but noticed that the temp was reaching 220 at idle and 190-195 0n the highway. It had a 195F t-stat so i replaced with a new 180F. Did not help. I also replaced antifreeze with new 50/50 mix. no change. I even purchased another temp gauge thinking it was old and inaccurate but not the issue. In my old set up I only had an idiot lamp so I dont have a reference. Timing is set at 0 @ idle so timing is not the issue. The only thing different from my truck and the new truck is the radiator. If the truck runs cool (190-200) but hot at ideal (195-225), would that be the radiator or maybe the waterpump. The pump does not leak nor makes noises and seems to push the water through properly. I need someones experience as I dont want to damage it. The sending unit is connected on the head located at drivers side front. I couldn't swap radiators because the motor went from a 69 c10 to a 64 chevy truck. thanks for any advice.

geezer#99 · 10-17-2010, 10:02 PM

IMHO timing is the issue. Retarded to 0* makes it run hot at idle. Run at least 8* with a points ignition or 12* with an HEI. And make sure your vacuum advance is working.

ChevLoRay · 10-17-2010, 10:07 PM

The engineers will tell us that there is a temp that is optimal for efficiency, but the seat-of-the-pants in us will counter that just about every time.

Radiators, fans, fan clutches, and shrouds should all be considered, in addition to any issues with timing. Having the fan correctly placed in the shroud will make a difference in how the air moves through the radiator.

DaSchlange · 10-17-2010, 10:11 PM

I am only guessing here, but those 250s, I have two of them, do not run that great on simply just average temperature. They are bad in cold weather just like most old motors so maybe they run a little hotter than others on average? Plus I'm doubting you have a fan shroud since most bottom line 250s didn't come with one.

NicoSlam · 10-17-2010, 10:44 PM

I do not have a shroud which I agree will improve the temp but is that the reason for the high temp. I set the timing at zero for MT only because the specs specified. I will bump it up to 8 and see what it does. The HEI distributor is new and the vacuum is working. thanks for your thoughts and advice.

DaSchlange · 10-17-2010, 10:52 PM

Well, yes I would say the shroud will make a huge difference. A full shroud will direct all of the fan's output directly toward the radiator. Without a shroud, all that wind will go elsewhere. Now that I kind of think about it, I would bet money that's what it is. Because you said once you get going down the road the temperature goes down. So maybe your radiator is getting the airflow it needs to stay cool while the truck is moving. So I would definitely start with a cheap shroud. Not that they are that cheap...or maybe a dual electric fan set?

10-17-2010, 07:55 PM	#1
NicoSlam Registered User Join Date: Nov 2009 Location: San Antonio TX Posts: 251	250 wATER TEMP QUESTION I installed my old 250 in another truck that had auto meter gauges. I got it running just as it did in my truck but noticed that the temp was reaching 220 at idle and 190-195 0n the highway. It had a 195F t-stat so i replaced with a new 180F. Did not help. I also replaced antifreeze with new 50/50 mix. no change. I even purchased another temp gauge thinking it was old and inaccurate but not the issue. In my old set up I only had an idiot lamp so I dont have a reference. Timing is set at 0 @ idle so timing is not the issue. The only thing different from my truck and the new truck is the radiator. If the truck runs cool (190-200) but hot at ideal (195-225), would that be the radiator or maybe the waterpump. The pump does not leak nor makes noises and seems to push the water through properly. I need someones experience as I dont want to damage it. The sending unit is connected on the head located at drivers side front. I couldn't swap radiators because the motor went from a 69 c10 to a 64 chevy truck. thanks for any advice.

10-17-2010, 10:02 PM	#2
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,736	Re: 250 wATER TEMP QUESTION IMHO timing is the issue. Retarded to 0* makes it run hot at idle. Run at least 8* with a points ignition or 12* with an HEI. And make sure your vacuum advance is working.

10-17-2010, 10:07 PM	#3
ChevLoRay Old Skool Club Join Date: Jun 2001 Location: Benton, AR "The Heart of Arkansas" Posts: 10,880	Re: 250 wATER TEMP QUESTION The engineers will tell us that there is a temp that is optimal for efficiency, but the seat-of-the-pants in us will counter that just about every time. Radiators, fans, fan clutches, and shrouds should all be considered, in addition to any issues with timing. Having the fan correctly placed in the shroud will make a difference in how the air moves through the radiator. __________________ Member Nr. 2770 '96 GMC Sportside; 4.3/SLT - Daily driven....constantly needs washed. '69 C-10 SWB; 350/TH400 - in limbo The older I get, the better I was.

10-17-2010, 10:11 PM	#4
DaSchlange Registered User Join Date: Sep 2010 Location: Gainesville, MO Posts: 251	Re: 250 wATER TEMP QUESTION I am only guessing here, but those 250s, I have two of them, do not run that great on simply just average temperature. They are bad in cold weather just like most old motors so maybe they run a little hotter than others on average? Plus I'm doubting you have a fan shroud since most bottom line 250s didn't come with one.

10-17-2010, 10:44 PM	#5
NicoSlam Registered User Join Date: Nov 2009 Location: San Antonio TX Posts: 251	Re: 250 wATER TEMP QUESTION I do not have a shroud which I agree will improve the temp but is that the reason for the high temp. I set the timing at zero for MT only because the specs specified. I will bump it up to 8 and see what it does. The HEI distributor is new and the vacuum is working. thanks for your thoughts and advice.

10-17-2010, 10:52 PM	#6
DaSchlange Registered User Join Date: Sep 2010 Location: Gainesville, MO Posts: 251	Re: 250 wATER TEMP QUESTION Well, yes I would say the shroud will make a huge difference. A full shroud will direct all of the fan's output directly toward the radiator. Without a shroud, all that wind will go elsewhere. Now that I kind of think about it, I would bet money that's what it is. Because you said once you get going down the road the temperature goes down. So maybe your radiator is getting the airflow it needs to stay cool while the truck is moving. So I would definitely start with a cheap shroud. Not that they are that cheap...or maybe a dual electric fan set?



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