460 overheating
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Junior User
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From: Renfrew Canada
460 overheating
This has been giving me a headache for some time now.
The engine, '78 460, .030 over, RV cam, about 9:1 compression, timing chain installed straight up, big headers, 4 barrell carter AFB carb 625cfm, 4 core rad, 7 fin flex fan.
The problem is heat. Without a thermostat the temp gauge never moves, hot day heavy trailer uphill, no matter it stays cold.
As soon as I install a thermostat she overheats, even at -40 in the winter. I figure the problem must be coolant flow, but I am unable to get a highflow thermostat and all the other ones have the same small passage.
Has anyone experienced similar problems? Help:-(
The engine, '78 460, .030 over, RV cam, about 9:1 compression, timing chain installed straight up, big headers, 4 barrell carter AFB carb 625cfm, 4 core rad, 7 fin flex fan.
The problem is heat. Without a thermostat the temp gauge never moves, hot day heavy trailer uphill, no matter it stays cold.
As soon as I install a thermostat she overheats, even at -40 in the winter. I figure the problem must be coolant flow, but I am unable to get a highflow thermostat and all the other ones have the same small passage.
Has anyone experienced similar problems? Help:-(
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460 overheating
Overheats ?
It boils over > Blows steam out ?
Or are you going by the gauge that could be faulty ?
When it is supposedly hot:
Have you put a meat/candy thermometer to check for sure?
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It boils over > Blows steam out ?
Or are you going by the gauge that could be faulty ?
When it is supposedly hot:
Have you put a meat/candy thermometer to check for sure?
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From: in the country
460 overheating
[updated:LAST EDITED ON 13-Nov-02 AT 08:49 PM (EST)]If you feel its a lack of flow(inability to dissipate excess heat from the engine) the first "fix" that would seem to make sense would be to have your radiator "rodded Out" and flow tested and reinstalled along with a hiflow thermostat and see if that makes any difference..........fd
---------You should always run your engine with a thermostat as the engine needs asomewhat stable temperature environment to achieve long life and reliability....fd
---------You should always run your engine with a thermostat as the engine needs asomewhat stable temperature environment to achieve long life and reliability....fd 
Posting Guru
Joined: Jul 2001
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From: Gainesville, FL
460 overheating
Mag,
There maybe an optiuon for you. I have played a game while building race cars:
1. Find yourself a fender washer that fits in place of the thermostat.
2. Purchase a few of them and drill different size holes in them.
3. Exchange washers until you find the correct flow rate for your vehicle.
4. It works well on drag cars.
KingFisher
There maybe an optiuon for you. I have played a game while building race cars:
1. Find yourself a fender washer that fits in place of the thermostat.
2. Purchase a few of them and drill different size holes in them.
3. Exchange washers until you find the correct flow rate for your vehicle.
4. It works well on drag cars.
KingFisher
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From: Renfrew Canada
460 overheating
Thx for the reply guys
yes I have tried several different thermostats from different manufacturers as well. Same result.
The thermostat is installed with the bimetal spring inside the intake manifold, so it opens against the flow of coolant, which as far as I know is the proper way to install it.
I had the 4 core rad built for this truck when the engine went in it.
And I dont suspect the rad since without a thermostat the gauge never moves. Also I believe the factory gauge to be working properly since it does not move without a thermostat but responds the way you'd expect it to when I install one.
The rad will not boil over, which i attribute to the fact thats its working properly and cools the coolant as soon as it is able to flow through it.
I have experimented with drilling 1/8" holes in the thermostats to increase flow, which worked. The odd thing was that even a couple of holes would make the engine run really cold.
My theory on this is that the thermostat might not be able to open due to the waterpumps pressure, since it has to open against the flow.
yes I have tried several different thermostats from different manufacturers as well. Same result.
The thermostat is installed with the bimetal spring inside the intake manifold, so it opens against the flow of coolant, which as far as I know is the proper way to install it.
I had the 4 core rad built for this truck when the engine went in it.
And I dont suspect the rad since without a thermostat the gauge never moves. Also I believe the factory gauge to be working properly since it does not move without a thermostat but responds the way you'd expect it to when I install one.
The rad will not boil over, which i attribute to the fact thats its working properly and cools the coolant as soon as it is able to flow through it.
I have experimented with drilling 1/8" holes in the thermostats to increase flow, which worked. The odd thing was that even a couple of holes would make the engine run really cold.
My theory on this is that the thermostat might not be able to open due to the waterpumps pressure, since it has to open against the flow.
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From: Renfrew Canada
460 overheating
Another bit of the puzzle.
It never overheats at low speeds or idling.
Also if I keep it around 2100rpm (80km or 50mph) on the highway, it is fine.
But over about 2100 rpm the heat slowly creeps up till it goes off the scale (if I let it). When it gets hot, I put it in neutral (clutch) and let it idle down, even for only 3-4seconds. Let out the clutch and get back on the gas, the gauge will slowly return to somewhere in the middle of "normal". Until 2-3 minutes later I have to repeat the procedure.
I have heard of rad hoses collapsing (VW jetta turbo diesel shop manual). I just ordered a new hose, i'll install it tomorow and see.
I'll keep you posted.
It never overheats at low speeds or idling.
Also if I keep it around 2100rpm (80km or 50mph) on the highway, it is fine.
But over about 2100 rpm the heat slowly creeps up till it goes off the scale (if I let it). When it gets hot, I put it in neutral (clutch) and let it idle down, even for only 3-4seconds. Let out the clutch and get back on the gas, the gauge will slowly return to somewhere in the middle of "normal". Until 2-3 minutes later I have to repeat the procedure.
I have heard of rad hoses collapsing (VW jetta turbo diesel shop manual). I just ordered a new hose, i'll install it tomorow and see.
I'll keep you posted.
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460 overheating
If you don't already have an actual temperature gauge you would probably be well served to install one of some type, just a thought , fd
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460 overheating
A single 1/8" hole is max for a thermostat bypass.
Have you checked your thermostat for operation? When a cold engine is first started you should not have any flow visible in the radiator (except the dribble thru the little hole). You can observe the flow and keep your hand on the upper hose to check the operation of the thermostat. If the thermostat is operating properly you need to look elsewhere.
Do you have a new water pump with the impeller on in the proper direction?
Put the OEM clutch fan back on.
Make sure your OEM fan shroud is on properly, without a shroud your truck will overheat.
Make sure your radiator support is properly sealed in order to force the air thru the radiator at highway speeds. If the air can bypass the radiator your truck will overheat. The air will take the path of least resistance.
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Have you checked your thermostat for operation? When a cold engine is first started you should not have any flow visible in the radiator (except the dribble thru the little hole). You can observe the flow and keep your hand on the upper hose to check the operation of the thermostat. If the thermostat is operating properly you need to look elsewhere.
Do you have a new water pump with the impeller on in the proper direction?
Put the OEM clutch fan back on.
Make sure your OEM fan shroud is on properly, without a shroud your truck will overheat.
Make sure your radiator support is properly sealed in order to force the air thru the radiator at highway speeds. If the air can bypass the radiator your truck will overheat. The air will take the path of least resistance.
Thanks for using FTE!
[font color=red]As a Moderator I do not "Subscribe" to most topics,
please send email/pm if you need a reply -Thanks![/font]
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Thread Starter
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Junior User
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From: Renfrew Canada
460 overheating
A gauge that the temp in degrees wouod be nice, and I will probably install one, I'm just trying to keep te dash stock.
It has a shroud which works well, a clutchfan won't fit since the 460 conversion, it sitts way to close to the rad, and too far inside the shroud.
The new hose made no difference, oh well...it needed replacing
anyway. I also installed a new rad cap and another thermostat. This one is a 160 degree highflow stat.I towed a trailer for a few hundred kilometers and kept an eye on the temp.
Same problem. Aroung 2100rpm the temp is good, lower with the 160 stat than with the 180 I had before, I think the gauge works.
As soon as I go faster....temp goes up, way up.
Do you think its possible that the pump, which is about a year old,
makes too much pressure, when it spins fast, for the thermostat to open against?
It has a shroud which works well, a clutchfan won't fit since the 460 conversion, it sitts way to close to the rad, and too far inside the shroud.
The new hose made no difference, oh well...it needed replacing
anyway. I also installed a new rad cap and another thermostat. This one is a 160 degree highflow stat.I towed a trailer for a few hundred kilometers and kept an eye on the temp.
Same problem. Aroung 2100rpm the temp is good, lower with the 160 stat than with the 180 I had before, I think the gauge works.
As soon as I go faster....temp goes up, way up.
Do you think its possible that the pump, which is about a year old,
makes too much pressure, when it spins fast, for the thermostat to open against?
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460 overheating
Since you indicated that the 460 moved the fan alot closer to the radiator , i'm just wondering out loud if maybe there is some resulting physical speed which corresponds with the radical rise in engine temp above 2100 rpm whereby the additional airflow over the radiator maybe Inhibited rather Enhanced by the fan being so close to the radiator and also the fact that you don't have a fan clutch to assist in additional cooling-----there has to be a logical reason that your engine can't dissipate the additional heat from the engine.......Somebody just has to be smart enough to figger it out , .....fd
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Joined: Nov 2002
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From: Shirley USA
460 overheating
Funny thing, I had just about the same exact circumstances and symptoms when I swapped a 460 into my 78 F250 in place of it's 400... I have a cooling genius who also happens to be a very honest guy local to me and I asked him to take a look at it. He took one look at it and noticed what I failed to see, the lower radiator hose was about 2 inches too long now that the water pump is closer to the radiator which created the slightest(not noticeable to me) kink at the bend of the lower hose. He told me to cut two inches off it, put it back together, and if that didn't work he said to come back and see him and he'd flow test the radiator... I haven't had to see the guy in 6 years now and my 460 stays nice and cool at idle with a unmodified thermostat installed.
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From: Louisville,Ky.
460 overheating
If the fan is too close, then you probably used the wrong holes in the frame for the motor mounts. I did the first time. I have since moved the engine back where it belongs and the clutch fan works fine.
You may want to check to see if maybe you have a head gasket leaking compression into the cooling system. I had a 440 Road Runner that did that once. It never lost water, but it would buld up excessive pressure in the cooling system causing it to get hot. With the engine cool, remove the spark plugs. Remove the radiator cap. One by one, fill each cylinder with compressed air(about 100psi). Check the radiator for bubbles. If no bubbles, Your ok, if bubbles, you are getting compression into the cooling system. It could be a cracked block, head or a head gasket.
Hopefully this is not the case, but it is worth investigating.
You may also want to check the 385 Series forum for help also.
Jimmy
You may want to check to see if maybe you have a head gasket leaking compression into the cooling system. I had a 440 Road Runner that did that once. It never lost water, but it would buld up excessive pressure in the cooling system causing it to get hot. With the engine cool, remove the spark plugs. Remove the radiator cap. One by one, fill each cylinder with compressed air(about 100psi). Check the radiator for bubbles. If no bubbles, Your ok, if bubbles, you are getting compression into the cooling system. It could be a cracked block, head or a head gasket.
Hopefully this is not the case, but it is worth investigating.
You may also want to check the 385 Series forum for help also.
Jimmy
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Joined: Jul 2001
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From: Miles City
460 overheating
How long since the motor swap/radiator recore?How long after the swap did you start having problems?
I swapped a 429 into a 75 F150 several years ago.The coolant in the donor car was horrid so I flushed and reflushed everything,plus got the radiator recored.Customer came in 3-4 months later,heater core leaking.Coolant was nasty again so reflushed 3-4 times.Several months later,summer is here and truck overheats at freeway speed but OK at idle.Owner babies it along until he blows head gasket.I pull motor to rebuild-coolant is vile again!I take radiator in for flowcheck-80% plugged.Looking in the top,the cores didn't appear to be plugged but obviously were.I'm wondering if the increased pressure from no thermostat would push coolant through restricted passages enough to cool.It might have been the head gasket all along,too.Just a couple thoughts-good luck.Keep us informed-I'm intrigued!
I swapped a 429 into a 75 F150 several years ago.The coolant in the donor car was horrid so I flushed and reflushed everything,plus got the radiator recored.Customer came in 3-4 months later,heater core leaking.Coolant was nasty again so reflushed 3-4 times.Several months later,summer is here and truck overheats at freeway speed but OK at idle.Owner babies it along until he blows head gasket.I pull motor to rebuild-coolant is vile again!I take radiator in for flowcheck-80% plugged.Looking in the top,the cores didn't appear to be plugged but obviously were.I'm wondering if the increased pressure from no thermostat would push coolant through restricted passages enough to cool.It might have been the head gasket all along,too.Just a couple thoughts-good luck.Keep us informed-I'm intrigued!
