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please help....anyone...have a 340. I rebuilt it in 05.from then it has over heated terribly,every time I try to run it . consensquently I parked it and all but forgot it.from an accident prior to me owning the car,a six cylinder radiator was installed,when I rebuilt the motor I changed it back to a v8 radiator.upon rebuilding of course ,a new water pump was installed along with hoses and belt.that is all that's changed.since rebuild,the lower rad hose collapses.last month I tore it down,replaced head gaskets and added a heavy duty(believe it)lower rad hose. it no longer collapses but still over heats. radiator seems to be primo condtion,very clean far as I can tell.thermostat is out. timing is 2-3 btdc.stumped totally.any ideas??? anyone.......help.
 

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Did you run it with the 6-cyl radiator before the rebuild, enough to know if it overheated before the rebuild?
Lower hose collapsing means that either the spring inside it broke/rusted away, or thermostat was stuck shut - too much suction.

Does it overheat when sitting at idle, not being driven? Or only while driving? Does power level feel normal?
And are you relying on the gauge reading to tell it overheats, or is it obvious physically - steam, feels too hot, etc.
 

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Probably a stupid question, but I'll ask anyway. Are you running straight water in it, or the recommended 50/50 mix of antifreeze and distilled water? Got a fan shroud around the radiator or is it wide open? Clutch fan or rigid fan and how many blades?
 
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run it for years with the 6 radiator.upon rebuild the stock(old) hose was discarded along with the spring, new hose had no spring.the newest hose is a heavy-duty ugly flex hose,doesn't collapse though. will over heat just at idle.with cap off..it appears to have decent circulation,I'm leaning towards getting the radiator looked at anywayjust to rule it out.getting a new fan clutch tomorrow,grasping at straws.......
 

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Lower hose has to have a spring in it for reinforcement, or the pump suction will collapse it, so that is not unexpected.
Is it running a 50/50 antifreeze mix? And the cap has to be on to prevent boilover, anyway. If the cap isn't there and working to build pressure, boiling point will be too low.
 

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Probably a stupid question, but I'll ask anyway. Are you running straight water in it, or the recommended 50/50 mix of antifreeze and distilled water? Got a fan shroud around the radiator or is it wide open? Clutch fan or rigid fan and how many blades?
oops yah six blades....
 

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You could also be running lean. Have you rebuilt the carb, make sure there isn't a bunch of junk sitting in the bottom where the jets are (stock carb carter designs). Put a 180 thermostat in her for starters, drill a 1/16th inch hole in the face to help purge air bubbles (won't affect the thermostat, flow is too low with the tiny hole), and make sure the idle screws are both at 1.5 turns out, and yes, radiator shroud.
 

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You could also be running lean. Have you rebuilt the carb, make sure there isn't a bunch of junk sitting in the bottom where the jets are (stock carb carter designs). Put a 180 thermostat in her for starters, drill a 1/16th inch hole in the face to help purge air bubbles (won't affect the thermostat, flow is too low with the tiny hole), and make sure the idle screws are both at 1.5 turns out, and yes, radiator shroud.
Its hard to imagine the carb stuff ,buti guess the time thing probably gotto it.i'll give em all a try thanks senior
 

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Discussion Starter #9
Lower hose has to have a spring in it for reinforcement, or the pump suction will collapse it, so that is not unexpected.
Is it running a 50/50 antifreeze mix? And the cap has to be on to prevent boilover, anyway. If the cap isn't there and working to build pressure, boiling point will be too low.
yes 50-50.and I did purchase a new cap.no on the spring, couldn't find one as yet.looking though...
 

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You want a thermostat in place. Running without one can cause overheating.
Do you have good circulation out the top hose? A collapsed bottom hose could be radiator core restriction.
 
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Most preformed hose I ever bought came with the spring inside, usually only bottom hoses. Don't recall ever seeing springs for flex hoses as they are built into the flexible coils. Lots of great info to work with here ,but start at the beginning with the radiator. It may have to be rodded by a Radiator shop to know it's clean. How is the flow through the heater core also?
 

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yes 50-50.and I did purchase a new cap.no on the spring, couldn't find one as yet.looking though...
Hose spring should be molded into the hose itself, it's not a separate item. You can feel it by pinching it. Those accordion hoses are junk, don't use them, use only molded hose. Costs more, but will last.
 
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Wild stab. Did you get a wrong rotation water pump? Pumps for both rotations look the same outside but vanes are set the opposite direction.
 

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Hose springs were a separate item when that engine was new. Might want to try a leak down or compression test to check for head gasket, Overheating at idle points in that direction.
 
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