Technical Overheating head scratcher

I'm new to the H.A.M.B. but have read many posts here and hoping for help! I have a '40 dodge coupe that I "finished" several years ago. I have never been able to drive it far due to overheating. I put in a 392 hemi, which is a stock rebuild with new stock water pump, and have a 64 ford 4 core radiator and electric fan. The strange thing is it will idle all day and be fine driving in town under 45 mph. As soon as you hit highway speed it begins to slowly heat up, and up, and up. When you slow down it will eventually cool off again. I've double checked the timing. I tried taking the hood off thinking it could be an air flow problem. I've tried different thermostats. Tried no thermostat. All the same result. More recently I pulled the radiator and had a shop put larger inlet and outlet on it and that seemed to help, but not solve the problem. Half the people I talk to think I need to restrict the coolant flow, that I might be cavitating in the water pump creating air bubbles, and the other half think a high flow water pump might help. Everyone seems to think the radiator should be adequate, but I'm starting to think its just too small. Although I really can't get anything bigger in there. I've tried the water wetter products, and also made air dams to force more air through the radiator. I'm kind of stumped at this point and would love another idea to try!

 

I agree with you, your radiator doesn't seem to have enough capacity.

 

Do you have a fan shroud?

 

Did it get worse when you tried running without a t-tsat? If it did not, I doubt restricting the flow would help.

Sounds like Radiator..but..

Just for grins, try cranking the timing a lot further advanced by ear. And more importantly, wait for the early Hemi guys to get better advice.

At highway speed-only issues, a shroud is not that important...because he is fine at idle and low speed where a shroud is sometimes needed.

 

It sure seems like it. I know plenty of guys who have used similar sized radiators on SBC applications, and even the radiator shop, who has been around town for 50 years said he has seen lots of similar applications. I've briefly looked into some custom aluminum radiators...but hoping to avoid that!

 

Air in the system? Is the radiator the high point?
My truck did the same, I drove up on car ramps and ran it with the cap off and it burped a couple times and never had that problem in years. Where are you in Nebraska? I'm in Omaha.

 

Yeah good point. Electric fan...sure its turning on at speed? Is it a pusher or puller? The only reason I suggested the shroud was at speed the air seems restricted or dirty. A pusher fan can do that.

 

Different\no thermostats made no difference. I actually have tried advancing timing, and retarding just for sake of experimenting. No change.

 

Overheating at speed, too small of a radiator. Once you get over 45, the load on the motor increases. More load, more heat.

 

It is a pusher fan. I could try a puller...but was under the assumption that fans shouldn't be much issue at speed.

 

Radiator is about a foot above the motor, so don't think its an air issue. I'm south of Omaha about 30 miles! Always good to know another local rodder!

 

Also......Post up the overbore size if it is bored, for when the Hemi guys see this.

 

Try taking the fan off.

 

Not an issue cooling at speed but it could be negatively effecting cooling by blocking and disturbing air at speed. I'm just guessing Steven, but I kinda figured that pusher fan revelation was coming.

 

See you're looking for a desoto door panel. I have a 56 hardtop and found a place that had the original materials. I don't much for extra parts, but have the old upholstery if you are looking for patterns. Might have an arm rest.

 

I like it. That's an easy enough thing to try! Just need to wait for some snow to melt!

 

Snow? Where you from? I'm golfing tomorrow. I love golfing on my birthday. It doesn't happen every year around here.

 

99 times out of 100...it's restricted flow of either air or water.
Was the radiator actually produced in 1964, or is it a newer replacement? Are you sure that it flows water well? Remove the radiator cap. Remove the lower rad hose. Does the water come out in a torrent and the radiator empty in like 4 seconds? It should.
Or this. Cold engine, no thermostats. Upper radiator hose disconnected from the radiator. Start engine. Should again be a torrent of water-flow.
Are the fins of the radiator bent and restricting air-flow? I had a '47 Ford. The flathead would overheat. Not the engine's fault. The radiator fins had at some point been introduced to the fan when the engine was running and it bent and flattened a whole bunch of the fins. Took hours, but I straightened every fin. But I also noticed the radiator wasn't emtying real fast. Found a soggy mouse nest or two. Cleaned out the radiator real good. Never overheated after that.

 

Near Omaha. Low of 1 day after tomorrow. No golf for me!

 

No its a new radiator. Water flow through radiator is fine. I did have a creative lower hose set up at one point, but straightened that out when I redid the radiator outlet. I used an appropriate sized pipe and short hoses, as someone had suggested the lower hose could be collapsing. Again, that helped, but not quite enough.

 

0.030 overbore. My dad is a long time mechanic and machine shop guy. He taught me long ago that you're taking a chance on overheating if you go to 0.060 on some motors.

 

The pusher fan is an obstruction at highway speed.

 

It seems like you've addressed most of the common causes for over heating. I had the same prob with a OT car several years ago. Seems that the engine bay was fine for the original engine but the one I put in it generated a lot more heat and took up more room in the engine compartment. Ran fine around town but on the freeway, it'd heat up, especially on warm days. Discovered that the engine bay, with the larger engine, wasn't allowing enough air to flow out of it. Sure, there was plenty of air available to the radiator but at speed, the air passing under the car caused a stagnant pressure pocket in the engine bay which wouldn't allow air to exit under the vehicle and the smallish air exits in the inner fender wells couldn't pass enough air to keep the air to the radiator flowing efficiently. I ended up making an air dam under the radiator to keep from having a low pressure area in the engine bay as well as opening up the fender wells. Did the trick. Just a thought.

 

Thanks! I did the air dam thing too. After that tried removing the hood, as I figured that should test the air blockage theory. That big motor does taken up a lot of space!

 

Steven....I don't pretend to know what's wrong with your car but I know my brother used a 64 T-bird radiator in an O/T Morris minor with a 406 SBC and he experienced the same trouble. He tried electric fans, shrouds, etc etc and he could never get the damned car to cool properly. As far as I know the problem was never resolved but I always suspected the radiator.

 

I had a 64 Galaxie do the same thing. I know you said the radiator is new but on mine it was plugged tubes in the middle of the core.

 

Decades ago had a slant six Valiant with the same problem. Changed hoses, thermostat, coolant, etc. Drove me crazy. I put a new fan belt on and the problem went away. The old fan belt didn't look bad.

 

Are you getting your readings off your gauge or off a portable temp reader. My stock 427 in my car runs about 220 on the gauge. Been like that for 15 years. No problems yet. Changed from a open system to a closed system with an overflow tank. No more puking out fluids. When changed to a closed system, I blew a few of the old hoses(more pressure on the system), put new ones on and problem solved.

 

Yes on the gauges, and verified with independent measurement. It will run about 220, which doesn't scare me too much, but the occasional boil over gets annoying. I can drive between 5 and 25 miles before it gets to be a problem depending on how hot it is that day.

 

A couple of pictures of the installation may be good. Sometimes we miss the obvious.