Hot Temp Running

[FirstEliminator]

   Hi,
    Been a while since I've been on here. For the past few seasons I've been driving my 68 Colony Park with the 483. This car consistently runs hot. Usually cruises at 215-220, sometimes 225. That's running 75 mph at 2400 rpm. The air temp has to be in the 50's for the thermostat to regulate at 180. The radiator has been recored with a new "high efficiency" core---or I paid the extra 300 for a name.
    One of the things that helped knock down the temp by about 10-15 degrees was to shut off coolant flow through the heater core. Without a blower fan moving air over the core, the hot coolant is circulated back into the block essentially bypassing the radiator. My car should have a heater control valve, but it was not installed. One heater hose was clamped shut with pliers to realize the improvement.  While I haven't done anything about it yet, I wonder if the bypass tube between the manifold and water pump can be too big? As it would also allow hot coolant to recirculate into the engine. I believe there needs to be some form of movement to stabilize temps across the engine. However, can this bypass tube be restricted down a bit to force more coolant through the radiator? I recently bought a used manifold that had the bypass totally blocked. Again, I feel coolant movement is beneficial to temp balance. Hmmm...I wonder if the bypass could be blocked if a few holes were drilled in the thermostat base plate to allow circulation?------thoughts?
    The car uses '65+ 427 cast headers. Pondering the possibilities, these headers have quite a bit of mass and will be over 400 degrees. I feel that heat is traveling right into the heads. After turning off the engine, the temp will hit 250. It seems there is a lot of stored heat in the exhaust manifolds that is balancing out the engine to a hot soak temp higher than it should be.  Has anyone else found the long cast iron manifold/headers to cause higher running temps?

   

   

[Tunnelwedge]

That's pretty warm. On the highway it should run at 190ish with just air flow through the rad.
I would look at the rad. Might not be as "high efficiency" as you think.

[machoneman]

Is it a reliable mechanical temp. gauge and not the OEM Ford dash gauge? 

[GerryP]

You need to isolate the source of the overheating.  It can be caused by the engine or by the cooling system.  This is where a heat gun comes in handy.  You need to see the temperature deltas between the coolant temperature going into the engine and that temperature out of the engine.  Then you need to see the coolant temp at the radiator inlet and the radiator outlet.  Then you need to see what the coolant temperature is as it moves through the radiator.

Your theories on this are imaginative.  But you're not going to find the problem there.

I encourage you to do some online research on cooling system operation.  It's more technical than just running coolant in a closed system.  You need to understand how a radiator works and how much heat it can remove.  I know you're looking for an easy answer or ideas on what to do but it just ends up as shooting in the dark and hoping you hit something.  If you want to do that, look at how well your radiator is sealed to the core.  You want all the airflow hitting the core to go through the radiator and gaps between the radiator and the core allow air to pass around the core.  The tattletale here is that you get no overheating sitting still or at low speed but starts overheating at higher speed.  That's not an absolute, but it is a clue.  On the engine side, look at your ignition timing.  Retarded ignition timing causes a late burn which ends up just heating up the exhaust port and the coolant.  And a lean fuel mixture can also cause overheating since a lean mixture burns slower.  It's also possible you have an inefficient water pump that doesn't create enough block pressure.  You might see that with one of those stamped steel pump impellers that has some defects, but that's a long shot.  And it could also be mismatched pulleys or a slipping fan belt.  Lots of stuff.  That is why you need to find out if the problem is radiator or engine side.

[cjshaker]

I'll add that, to my understanding, that bypass is there to keep the pump from building too much pressure before the thermostat opens. Probably not a good idea to just plug it unless some sort of adjustable regulator is used, that allows coolant to flow at all times. Also, some of those "high efficiency" cores are just a bunch of added tubes, which can actually impede airflow through the radiator to the point that heat transfer can't take place as it should. Not saying that is the issue, but it has been a known problem with some. I'd follow Gerry's advice and track down the issue with careful temp readings, although that can be a challenge since it's happening at speed. One more thing....do you have a shroud?

[FirstEliminator]

Yes, to shroud, clutch fan, mechanical temp gauge and EFI temp sensor. Timing is where it should be, A/F is easily adjustable with the efi----made no difference on temp. Aluminum high flow pump. Belt not slipping. Pulleys are all stock.

   It does get hot sitting still. At low speeds like 30mph is best case scenario but still above thermostat...usually 190-200.

   I have a thermal imaging camera and did not see anywhere that was a concern. It's been a while since I've used the camera, so I should look again to see the temps. Last time, all cores were flowing.

[jayb]

I don't believe that the bypass tube is there to prevent pressure buildup, it is there to keep coolant circulating through the engine before the thermostat opens.  If the bypass is blocked and the thermostat is closed, the coolant doesn't have a way to circulate, and you will get hot spots in the coolant before the thermostat opens.  A long time ago, before I learned that you should drill some small holes in the thermostat if you plug the bypass, I would watch the temperature gauge as the engine warmed up with the bypass blocked.  The temperature would very slowly climb to the thermostat opening point.  Then, as soon as the thermostat opened, the temp gauge would peg at 240 degrees for a few seconds, before coming back down.  Pretty sure what was happening was that there was a bunch of really hot water in the heads that couldn't get out, and when the thermostat opened it would all rush past the temperature sender before cooler water from the radiator finally hit the sender.

[Falcon67]

Try running a 195F thermostat and see if that changes things.  For whatever reason, your "recored with a new "high efficiency" core" is not transferring heat out of the engine very efficiently.  If you're talking copper core and they put in a tight fin count/4 core then you've been - IMHO - had.  Been there, spent that, scrapped that. By the time the air gets to the 3rd and 4th core tube it's already hot and does little to no good. And a tight fin count is as much restriction as surface area, requiring hella fin displacement to pull enough air though it to work. 

[cjshaker]

Has it always been this way? Any possibility that one or both head gaskets were installed backwards, not allowing water to flow through the rear of the engine? Just a thought.

[Tunnelwedge]

Pulleys are all stock.

Maybe try an overspeed on the water pump. I use a small aluminum pulley.
I also use a brass stock rad with a small e fan and drove Mountain Road in Moncton at 6PM on Sat for the show.
Seen 220* in stop and go.
The Lane has an aluminum rad, it never gets hot.

[machoneman]

http://diyford.com/wp-content/uploads/2013/11/452.jpg

Check your tabs per this photo. Tabs must be present on each head facing down and clearly visible or...the gaskets are on backwards.

[FirstEliminator]

http://diyford.com/wp-content/uploads/2013/11/452.jpg

Check your tabs per this photo. Tabs must be present on each head facing down and clearly visible or...the gaskets are on backwards.

   Back when I put the engine together the FelPro gaskets were marked with front. I will take a look, but 99.9% sure they are correct.

[FirstEliminator]

Try running a 195F thermostat and see if that changes things.  For whatever reason, your "recored with a new "high efficiency" core" is not transferring heat out of the engine very efficiently.  If you're talking copper core and they put in a tight fin count/4 core then you've been - IMHO - had....

   The guy retired and closed shop a few months after I got the radiator. He had a good reputation, but who knows? I might try an aluminum radiator. Might as well put a 195 thermostat because it is in the 190's more often than at 180.

[My427stang]

The iron headers could absolutely be heat soaking the engine bay, especially if the timing is a bit retarded and generating heat and/or you have an exit airflow problem

1 - Be certain your fan isn't on backwards (silly but have seen it)
2 - Make sure your ignition advance at cruise is adequate
3 - You could make a small air dam under the bumper, maybe adapt something, that creates low pressure at speed to push the air downward
4 - If it is just heat soak, ceramic coating the manifolds could help.
5 - I have never seen a heater hose loop or bypass cause overheating.  The heater hose does go back into the pump, but it would cool the water somewhat, easy enough to buy a shutoff and splice it in. 
6 - The bypass I suppose could be restricted, or even eliminated if you had an adequate hole in the thermostat, but the area it provides is small compared to the thermostat hole when open, and with the pump pushing, I'd be surprised to hear that being an issue.   Be very careful though, if you restrict or eliminate too much, your heater core may not be happy.

With all that, if cool air allows it to run thermostat temp, I would think you have an airflow problem, could be too tight of fins in the radiator, backwards fan, or an exit airflow issue

[FirstEliminator]

Hi Ross,
    #5. heater hose loop or bypass....

   What made me consider this was reading about 351c in the Tom Monroe book,  ..."leaving out the brass plate could cause overheating due to too much coolant bypassing the radiator".  In the Colony Park, clamping off the heater hose would prevent hot water from being put back in the block so it would then only be drawing cooled water from the lower radiator hose. On a long trip back from Carlisle All Ford show it made a 10-15 degree difference. Over the 6 hour drive I took the clamp off and on to validate a difference. Definitely time to put the heater control valve back in place.

    Overall, the engine seems to make more heat than the radiator can handle. Is there something wrong with this radiator? I don't know.   To try an aluminum radiator would be a good test. Summit has a Griffin that claims "exact fit" for $907.  If aluminum is going to make the difference, great! But, I don't want to spend $907+ for no gain.
    Here is a possibility: I have a 68 Parklane pahts-cah. Maybe I will pull the radiator from it, have it checked out/cleaned. Then install it to see if there is a difference. If it makes no difference I have other cars to use it in.