340 running hot

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70orangeswinger

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My 1970 340 continues to run at about 210 or higher ever since I had it rebuilt. I have about 1000 miles on the motor. Radiator has been checked, new water pump, new hoses, still no luck. Could the head gaskets be on upside down or backwards?
 
Have you checked/adjusted the ignition timing? If it's not getting enough advance it will run hot.
That's where I would start.

Ted
 
70orangeswinger said:
My 1970 340 continues to run at about 210 or higher ever since I had it rebuilt. I have about 1000 miles on the motor. Radiator has been checked, new water pump, new hoses, still no luck. Could the head gaskets be on upside down or backwards?
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make sure you have an 8 blade water pump, or an 8 blade hd with the anti cavitation plate , If yours is a 6 blade that could likely be the reason it runs hot.
 
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Does it run that temp at idle in traffic, when running down the highway or both? Coolant or straight water?

Did you replace the cap and/or thermostat during the rebuild?

Oddly enough. When I last went through my engine, I had some cooling problems. The new cap and thermostat that I had installed were BOTH bad straight out of the box.
 
12many said:
make sure you have an 8 blade water pump, or an 8 blade hd with the anti cavitation plate , If yours is a 6 blade that could likely be the reason it runs hot.
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I installed a high volume water pump but I don't know how to tell if it is what you are recommending.
 
1968FormulaS340 said:
Does it run that temp at idle in traffic, when running down the highway or both? Coolant or straight water?

Did you replace the cap and/or thermostat during the rebuild?

Oddly enough. When I last went through my engine, I had some cooling problems. The new cap and thermostat that I had installed were BOTH bad straight out of the box.
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Engine runs hot all the time, even hotter in traffic. If you are driving for any amount of time at around 35 mph it cools down to 180-190. I have replaced the tstat twice and am now running a 165 degree. I tested the cap and it appears OK
 
Sounds like maybe the factory sticker which is too little. Try starting at 12 and experiment from there. Its hard to beat the factory fan setup.
 
180-190 driving at 35 is perfect. n9y is correct. advance timing to at least 10* advance at idle. running hot at slow traffic is a fan problem, my guess is a badly slipping clutch on the fan
 
OK, lets back up a bit. When you say that you haven't checked the vacuum advance, does that mean that it's not hooked up at this time?
 
had an issue with the lower induction hose from the radiator to the engine , it would suck down together and resrtict the water flow though it . made a stainless steel one out of weldind rod put it in the lower hose , flow returned temp went down . another had a swimming head on a head gasket . compression leak cause overheating issues . and did you mag all the parts for cracks in the cooling system before building ?
 
pomonamissel said:
had an issue with the lower induction hose from the radiator to the engine , it would suck down together and resrtict the water flow though it . made a stainless steel one out of weldind rod put it in the lower hose , flow returned temp went down . another had a swimming head on a head gasket . compression leak cause overheating issues . and did you mag all the parts for cracks in the cooling system before building ?
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Oh, good point. I forgot about that. Along with my bad "new" cap and bad "new" thermostat, I needed to add a spring to my lower radiator hose because my "new" hose didn't have one.

Here is a link for the hose spring. Yes, it's for a mustang but your radiator hose won't care.

Mustang Lower Radiator Hose Spring Stainless Steel Small Block 65-73
 
If all appears to be in order externally have an oil analysis done. And did the OP have a heating problem prior to the rebuild?
 
well garbage part a side , i like stainless welding rod for that spring , china parts you know . would want that spring or pieces of it in my waterpump . have you checked for co2 in your cooling system its a simple test . just running the engine with the cap off during operating temp , the system should not be puking any coolant during this test , if so your problems are bigger .
 
RustyRatRod said:
The thermostat is way wrong. It should be a 195.
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since it straightens out "at speed" either there is an airflow or a water flow issue assuming the timing ain't moderately or more retarded (my 85 318 is at 18 ported with 35 total set with the FBO $22 plate). Much more likely air flow. N9 is a cold racing plug but unrelated to it overheating and as said get a 195 in there.
 
Yes. This lower thermostat myth needs to go away. Look at it this way....

Let's say your car is ringing at 220 with a 180 stat. The 180 stat (if functioning correctly) is open at 220.

Now, if you put in a 160 stat in an attempt to solve the issue of the car running at 220, what happens?

Well, at 220, a 160 stat (if functioning correctly) will be open.

So. An engine running at 220 with an open 180 stat or an open 160 stat are the same.

You have done nothing but spend time and money to achieve the same end result.
 
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Just curious, Was it a Mopar Performance pump, with the description it was for iron heads/drag racing: this one as shown p5249558, or remember the part# and brand?

312-P5249558_3.jpg
 
I once had a new water pump that the lower hose outlet was never stamped out. It was blocked completely with flashing 3 inches up inside. Played hell finding out why this new motor was running hot. Since then I look at everyone and have found some restricted with flash and one that only had a hole the size of a dime to get coolant through.
 
Dana said:
I once had a new water pump that the lower hose outlet was never stamped out. It was blocked completely with flashing 3 inches up inside. Played hell finding out why this new motor was running hot. Since then I look at everyone and have found some restricted with flash and one that only had a hole the size of a dime to get coolant through.
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Correct. Always check a new water pump just like you would a cylinder head. This has happened to others. It doesnt take much of a restriction to cause a problem.
 
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