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Discussion Starter #1
Hey guys,

1966 coupe 289 v8 and c4 trans. The 289 was just rebuilt.

We fired her up yesterday for the break in but had to shut it off as it was getting too hot (~210). It has a new 3 row champion aluminum radiator, 2700 cfm electric fan and new edelbrock high flow aluminum water pump. After it ran for about 5 minutes, we shut if off and I felt the rad hoses... the top one was hot as hell and the bottom one wasn't even warm.

Is this a thermostat issue??? I can't think of anything else that would not allow the coolant to flow through the system. The t-stat is new and 192 degrees. Maybe I should put the old 180 degree one in cause I know for sure that it worked well
 

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If the top hose got hot then the thermostat opened and the pump is working. 192 is a better temperature to operate the engine as well as promote better cooling of the radiator.

It sounds like you have a clog somewhere in the radiator or downstream of it. First the obvious: check to see if the bottom hose collapses when the engine is running. Someone may have forgotten the coil spring that keeps the hose from doing that under the pump vacuum.

Hopefully someone didn't leave a rag or a piece of gasket somewhere.

Try this test: take the hoses off the radiator, stick a running garden hose in the top hole and see if the water runs easily through the radiator. Then continue testing downstream.

You can try to clear out a clog by backflushing. Do the engine by taking the thermostat out, reconnecting the top hose and connecting a garden hose to the lower hose. Backflush the radiator in a similar manner.
 

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Easy to put a thermostat in backwards. It does sound like it's defective, wouldn't be the first time. Always a good practice to put it in boiling water to make sure it's functioning. Candy thermometer works good for checking. Outside possibility that the head gaskets were put on backwards.
 

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Discussion Starter #4
Nah head gaskets are on right I triple checked that the word Front was at the front and that all cooling passages were lined up when I put them on. I am changing out the thermostat for sure tho.

What could cause a clog in a fresh engine with new cylinder heads and radiator?
 

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Have to be the size of a mouse to shut it off that bad. Only other thing that comes to mind is if temp sender is in water neck. Sometimes aftermarket senders can hit the thermostat preventing it from operating.
 

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Discussion Starter #6
Can't be that either the temperature sending unit is no where near the water neck its more behind the distributor. I'm hoping its just a thermostat problem. Could the heater core or heater hoses have anything to do with it??
 

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Take a piece of hose and bypass the heater core to check that real fast.
 

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make sure the actual temp gauge isnt screwed up.
 

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Discussion Starter #9
if there was any air in the system that would mess with the temperatur sending unit too right? my gauge is aftermarket (SunPro) not the stock gauge
 

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yeah, i would still make sure that thing isnt toast first before doing anything with the motor.
 

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If the top hose got hot then the thermostat opened and the pump is working. 192 is a better temperature to operate the engine as well as promote better cooling of the radiator.

It sounds like you have a clog somewhere in the radiator or downstream of it. First the obvious: check to see if the bottom hose collapses when the engine is running. Someone may have forgotten the coil spring that keeps the hose from doing that under the pump vacuum.

Hopefully someone didn't leave a rag or a piece of gasket somewhere.

Try this test: take the hoses off the radiator, stick a running garden hose in the top hole and see if the water runs easily through the radiator. Then continue testing downstream.

You can try to clear out a clog by backflushing. Do the engine by taking the thermostat out, reconnecting the top hose and connecting a garden hose to the lower hose. Backflush the radiator in a similar manner.
The spring in the radiator hose is a myth that many people think they need, and it's not. The springs were included in the radiator hose so a vacuum could be applied to the system in the factory to evacuate air after the car was filled with coolant and not collapse the radiator hose. Beyond that however, unless there is a malfunction somewhere in the cooling system, the normal operating pressure and vacuum of the system should not cause radiator hose collapse. Something else is going to be the culprit if this is observed.
 

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Discussion Starter #12
Yeah I've heard that same thing Lizer thats why I'm not too worried about not having a spring. I just dont understand how the lower rad hose could be so cool while the upper one is hot. I know the most obvious thing would be a clog but I dont see how that could have happened. Even though the heater core is hooked up to the cooling system isnt it more of a secondary path? Like the majority of the coolant flows through the engine/rad not the heater core?
 

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When the car is at temp, can you tell if the coolant is actually flowing/circulating, or is it just standing still?
 

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also do you have the correct direction water pump for the motor?
 

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Discussion Starter #15
When the engine got started and warmed up i could see the coolant moving through the radiator and it would occasionally spit out some. I tried burping the system by removing the heater hose going to the 90* elbow in the intake and coolant literally shot out. So I'm assuming the water pump is moving coolant...

The water pump is a standard rotation edelbrock aluminum one:

EDELBROCK WATER PUMP HI-FLOW 289/302/351W 1965-1969 | CJ Pony Parts

If I haven't set the timing yet could this also lead to it running so hot? Besides the fact that the lower rad hose wasn't getting hot
 

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Now was air coming out of the radiator when it was running?

Try a startup with cap off, and rev the engine slowly to double check the flow is increaseing and its like the engine is sucking the coolant right down.

Coolant Level proper for expansion?

Is the Heater core clogged?

the last thing that happened to me was my new radiator came with alot of Styrofoam casing, that flaked off and clogged the thing up without me knowing, and I had to constantly flush it till it all came out.

Is it overheating at idle or just reving?

Was the block bored 60 over?
 

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Discussion Starter #18
Okay so yesterday I swapped out the 192# t-stat for my 180* one, topped off the radiator with more 50/50 coolant and get the engine warm while burping the air out.

Now both the upper and lower hoses get hot and it holds around 190-195 idling and gets up to 205 with heavy throttle. The electric fan kicks on at 190 and I'm not running a mechanical one. The electric fan doesn't have a shroud althought I wish it did. Anyone know where you can get just a shroud for a 16" electric fan??

The engine was bored 30 over and it has edelbrock aluminum e-street heads. I'm gonna take the thermostat housing off today and drill two 3/16" holes in the t-stat to help the cooling some.

We got it running and out of the driveway. It got about 30 feet into the street and we heard clunk clunk clunk... a u-joint clip came out... sheesh
 

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Sounds like the thermostat was the main problem. I wouldn't bother drilling the thermostat. As the engine breaks in, temp should come down a bit. Focus on your airflow now.
 
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