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Discussion Starter #1
I'm just curious about this.

give a stock build up with avg. compression. what is the highest temp. a motor can get up to before stuff starts going to crap??

My brother has a 283SB w/305 heads in his Wrangler. (with all of the gearing it'll turn over all 4 12.5" tires!!) ANYHOW, He let it run one time wiht the electric fan off... walked away for ten minutes and came back to find the temp gauge at 250DEG. F.

Any of you seen higher numbers??

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The biggest problem is going to be the 305 heads, all the late model heads are thin castings to reduce weight and wont take much heat to crack.

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Leo Paugh
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The 250deg. you saw was due to "heat soak". When you shut down a motor the water stops flowing(carring away heat)and the heat that is still in the metal continues to flow to the lowest tempture(1st law of thermodynamics). The heat from combustion flows through the piston through the rings through the cylinder walls into the water etc.etc. roughly stated.

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Harley
69 461 El Camino Nitrous Model, 69 Chevelle coupe
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According to my 66's service manual, 245 deg is the maximum operating temp for a SBC. I'd take a look at the oil to see if it started breaking down. In fact, I'd change it anyway. Since engineers liks a safty factor, the engine may not have been harmed, but change that oil. As Chev64 said, the heads are the weak link here. If they are late model they could crack. If something seems amiss, get a pressure test done at a radiator shop.

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Pat Kelley
66 El Camino, daily driver
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Harley, I read it that the engine was running for 10 min without the fan running and reached 250 degs. Of course, you're correct about heat soak.

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Pat Kelley
66 El Camino, daily driver
67 El Camino, STRIP/street
 

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Discussion Starter #8
Harley, nice plug for the thermo knowledge


We changed the oil and checked all the other stuff... no problems. The 250 temp was just before shut off! I'm sure it rose to 260 after shut down... but it's a jeep so there is plenty of room to dissipate the heat. Our cars are like incubators for motor heat.

thanks all



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have now>>>>> am building
2.73 open 10bolt>>>>>>3.73 posi 12bolt
350>>>>396 w/nitrous
shooting for 12s in 1/4
college student budget!
 

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My small block 350 (see specs in my signature below)usually runs 220° max but rises up to 230-235° after it's shut-off. It's all stock, no late-model heads but it has an aluminum Edelbrock intake. I am going to be putting a stock cast-iron intake on soon- will that make it heat up more? Also, is 220° a little high for my engine?

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Robert, GM went to light casting in an attemp to reduce weight for fuel ecomony reasons. I'm guessing, but probably around 1974 or 75. It wasn't a very good idea. The weight/fuel saving were negligible and the heads became prone to cracking.

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Pat Kelley
66 El Camino, daily driver
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Discussion Starter #11
SHAWN,

I may be a little over causious on the matter. But if my temp. gauge read 220 *F I would pull off the road and open up the radiator to check for fluid!

During the summer I run a 165 thermostat which mioght be a little low. BUT things get pretty hot below the mason dixon line.
During the winter I run a 180 thermostate to help the motor stay warm enough so my heater is usefull.

I would try posting about that 220 temp. see what the others say... tell if it is stock or built etc....

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have now>>>>> am building
2.73 open 10bolt>>>>>>3.73 posi 12bolt
350>>>>396 w/nitrous
shooting for 12s in 1/4
college student budget!
 

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220 is not overheating, and no damage will occur. 250 - 260 is getting there, but if the coolant didn't boil out, there should be no damage at all.
 
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