Overheating 484 Hemi - Need Ideas

Been working on Mopars for 50 years and this one has me stumped. Cannot figure why motor is overheating. Please read carefully. The engine, original stock 426 Hemi block .060 over, 10.8 compression. 4.15 stroke crankshaft., 484 total cubic inches. Heads Mopar Performance Aluminum fully ported. Stock magnesium crossram intake with stock 780cfm crossram carbs. Camshaft .585 lift with 247 intake and 262 exhaust duration @ .050. Radiator 26" two row aluminum with dual 13" electric fans. Radiator was built by Superior Radiator a local rad builder. Claims it will handle 1000HP cooling. Engine has Mopar aluminum water pump with 165 degree thermostat. Upper and lower pulleys are same diameter. Running straight Prestone green as I have in all my cars without issue like this. Head gaskets are SCE copper if you need to know. What I have done so far. I have changed out thermostats and no change in overheating. Changed out thermo fan switch to kick on sooner. Noticed lower radiator was collapsing as engine RPM was increasing. Installed inner spring in lower hose still overheating. Checked spark plugs for possible lean condition, plug color was perfect. Suggested to pull out some timing from 34 degree total to 28 degree still overheating. Startup of engine will heat to about 190 degrees for a short time and continue to climb from there. Will hold at 210-225 depending on outside temp. If stuck in traffic for even a few minutes it will go to 230 and beyond. Running at high speed after getting hot will not drop temp but a few degrees. Any ideas to where I go from here? I am lost with everything brand new except block and intake. Pulling my hair out with not much left. See pic for radiator setup. Temp gauge is correct, when I came home from a drive outside temp was 78 degrees, temp gauge read 225, checked engine temp with laser thermometer. Block temp 228, heads 234, intake 118, radiator 185. Thank you for any ideas.

Are the fans spinning in the right direction?

The only thing is see is that plate on the rad holding the fans. That’s not a shroud. I tried that same thing on my old demon, ran hot with 4 puller fans. An engineer friend told me I needed a minimum of 3/4” deep shroud. I believe that plate is restricting air flow.

running straight anti-freeze isn't good. anti-freeze by itself isn't a good coolant. do a 50/50 mix. the higher the percentage of anti-freeze the worse the heat transfer. another thing i've found is water pumps do make a difference. flow kooler has been the best for me and the 440 source unit absolutely the worst.

1. Fans blowing in right direction.
2. Shroud something to look at, no room between fan and water pump pully on A body with hemi. May have to modify fan to make 3/4" gap. Current gap between radiator core and shroud in 3/8". rick Did moving shroud fix your issue?
3. Ran straight anti freeze in all cars, 600HP 500 inch wedge never went over 185 degrees in traffic. May have to try if shroud doesn't work. Yes pumps do differ. Ran the Mopar aluminum on all my cars without problems.

Thanks to all with ideas. Any others?

What is your temp difference between the top and bottom hose? And take temp readings all over the radiator to make sure there are no hot spots. Check your bypass hole in the water pump housing to make sure it is not too big. Check both sides of the water pump housing and both heads as it comes up to temp to see if they are even or if one gets hotter quicker. Maybe change the water pump pulley to speed up the water flow. I would pull the thermostat and see what happens.

The old adage that slow vehicle speed overheating is usually air flow related, while road speed overheating is typically a water flow issue doesn't seem to apply given your description.

20* drop top to bottom of the radiator in this application sound about right to everyone?

What you have is an air blocker. What you need is a factory style set up. I have a 528 with a factory set up and it doesn't get hot. The factory engineers spent a lot more time working things out than these fly by night fabricators. How many vanes does the water pump have? Does it have a anti aviation plate?

I didn’t catch the straight antifreeze. +1 to the 50/50 max. Straight H2O for the track.

71Bird. It has the factory style water pump and housing, the Mopar Performance is made out of aluminum and looks identical to the factory setup. 6 vane pump. Worked perfect in all other builds.

Is this a new build ? Or was fine then stared happening?

Have you started it cold with the cap off and watched the tstat open and water is flowing ?

Have you tried removing the stat and put just a restrict or in?

Heat gun the the rad top to bottom, and the hoses what’s it telling you .

Anything odd about performance? Pinging or sluggish?

If it just sat and idled would it boil?

Check the timing at idle , seem right?

It is making pressure right?

Your idle timing is too low...Total might be ok, but my guess is you have a pretty big spread between them. I use a Firecore distributor on my Hemi and I shortened the mechanical advance to about 8*....So it idles at 20-22*, and hits 30-32* at 2500 or above....Now your engine is smaller, and handle more total than mine, but it will like more timing at idle. As much as you can without having trouble starting it. Total on a 484 Hemi we were anywhere from 34-38*

Not sure how your car is set up, but just throwing this out there...I used to have an aftermarket trans cooler mounted in front of the radiator. The temp gauge was reading 200-210 when summer driving. Once I moved the trans cooler to a different location the temp range dropped a full 20 degrees.

Yes it did. I got a 1” shroud from wizard with 4 staggered spall fans( they just cleared the moroso electric water pump) . Engine temp was 175 highway, never went over 190 sitting in traffic when fans started up. Wizard told me a shroud should be no shorter than 3/4” deep coz it makes a high pressure in front of the rad which in turn forces the air faster through the openings by the fans. It worked for me.

Here's a thought. If you're running the exhaust manifolds, is the manifold heat riser valve opening as it should?

If you choose to move the shroud away from the core you can change the fans for low-profile. I don't think that's the issue. The fans and fan openings seem plenty big.

If the radiator is at 180* and the engine is at 230* then that sounds like a coolant flow issue and not an air flow issue. Where on the radiator did you take the temp? Make no assumptions about the new parts including the radiator's ability to flow. Take e temp at the upper hose leading into the radiator and at the lower hose. Too great of a drop in temp indicates a restriction. I don't have the number, but I would guess 50*f or greater.

Also, engine temp always goes up after shut down making them unreliable (irrelevant) for diagnostics. Did you take those readings after shut down or idling?

If the lower hose is collapsing, that's a good sign the water pump is moving a lot of fluid, but may also be indicative of a restrictive core.

Definitely move to 50/50 up to 70/30 and no less than 30/70. No greater on the concentration of coolant than about 70%. The heat capacity of the mix drops as the concentration goes up. 100% water gives the greatest heat carrying capacity, but no protection.50/50 is a nice compromise that's easy to remember and to mix. Lowest freezing point is achieved at about 65%. Water-wetter works. Water transfers and absorbs heat from the metal surface more efficiently that Ethelyn Glycol, or so they say.

I'd get rid of that cover over the back of the radiator. It looks like it is blocking about 1/2 the air flow. As a test, take that and the fans off, and put on a factory fan. See what happens.

I agree.

Can you mount the electric fans without using that plate on the back of the radiator.

Try a mechanical fan with a low profile viscous clutch. Hayden now offers a muscle car low profile unit.

Troy’s cross ram Hemi 68 barracuda and it the same setup in his Hemi 68 dart. It’s got a 3 row high density core brass radiator. It’s a stock setup and fits correctly.

I drill about four 1/8 inch holes around the T-stat. Then wile filling with fluid I jack the front of the car up until I see the heads obviously are up in the front to help air escape as the coolant is added.

Also you said the pullies are the same size so it's 1 to1. The water pump isn't spinning fast enough as well. Just another thing to check. I would check what size the HEMI pullies are supposed to be.

I had this same issue same basic set up you have , tried everything --ended up being a flubbed up distributor

I had overheating issues when I first put my sb Dart together. I tried running electric fans and they didn't work for me. In the end a Viscous fan kit from MP and a good shroud fixed it.

As others have mentioned check the inlet and outlet temp on the radiator along with the temp at the thermostat housing. I like Stant high flow thermostats and also drill four 1/8" holes on the flange.

Good eye! I went to check what I have and it's right about 3/4".

Untitled by Greg Ault, on Flickr

If It was mine I would try removing the existing fan and mounting plate, install a belt driven fan and test.
That alone should improve it, going down the road (but it will still heat up at low speeds due to the lack of a shroud).

I also used to use a pretty high antifreeze to water percentage (Michigan freeze protection) but went to 50/50 and
noticed a slight improvement. I'd suggest that later as well unless you're dead set against it.

A deeper shroud as mentioned should also improve it at low speeds, but if you look for one, try to find one that allows an airflow path for situations
where the car is moving 50+mph (as airflow through the grille from a car moving 50+mph is better than most any fan could provide).
Many aftermarket E-fan/shroud combinations don't have those provisions, and the fan usually ends up running constantly at higher vehicle speeds when it shouldn't be needed. In fact the fans can move slower than the air coming in through the grille, and potentially block some airflow.

Once any improvement is found, then the crossroads question is usually whether to revert to a more OE setup with belt driven fan and custom shroud, or stay with electric
and try to find a shroud with louvers or flaps that open at higher speeds and allow airflow.

I agree with removing the whole electric fan pieces, factory didn’t use that on millions of cars. Same with the aluminum radiator (are the tubes vertical or horizontal?) a friend had an all aluminum 528 Barton Hemi with same intake you got, aluminum rad with two big fans and the mezery pump, couldn’t keep it under 220. His dad had a 484 Hemi (stage 5 heads) with the cross ram and stock radiator-fan setup, ran 160 and never overheated didn’t even have a shroud.

Lots of those aftermarket electric fans don't move anywhere near the cfm they claim. Thats why a test with a belt driven, factory fan is in order.

Hard to say what the problem is until you try a few things. My guess is that those electric fans aren't pulling much air or it could be the flat plate that they are mounted on. Could also be a problem with the water pump or perhaps some other issue that is choking off the flow. As others have said I'd start by removing the fan assembly and bolting on a factory fan. See how that works and go from there.

The symptoms you are describing, almost bet its fan related.
Had nearly same issue with mine several years ago. Had a cheap, parts store fan on it and would heat up quickly on the street or the track.
Bought a GOOD fan, immediately fixed the issue.
By good, if a fan isn't pulling 20 amps or better, its motor isn't cutting the mustard. I have found Derale fans to be of excellent quality, and they are US made.
Having them on a relay(s) is also a good idea

Been working on moving the shroud back using some 3/4" aluminum angle for top and bottom and U channel for sides. Got everything done except the bottom, that will be for tomorrow. Everything has to be polished before installing, a little time consuming. Hope to test it out tomorrow when completed. Now have a full 1" between core and shroud. Hope it works. The fans were supplied by the radiator builder, he claims they are the best out there from his experience. Some guy builds them out of his garage somewhere in one of the Midwest states. The shroud has rubber flaps in bottom for high speed flow, same as used on the BeCool shrouds.

The Mercedes fan with Howie's controller is the absolute best electric fan set-up I have ever ran. Easily cooled my blown aluminum 505 Hemi in the Dart.

I don’t think I saw it posted, what are the cfm of those fans?

Forgot this, does your overflow tank have a pickup tube in side. Also I don’t see a vent hole in the tank. Under pressure antifreeze won’t go into the tank coz there isn’t air escaping the tank. If would happen to get in the tank there has to be a tube to suck it back into the rad. I drilled and installed 2 90* 1/8x barbed fittings with a clear hose to see the level of antifreeze in the tank.

Vent tube built into the bottom of overflow tank. Goes up to within 1" of top of tank to puke if necessary. Top tube go to within 1/2" of bottom to draw back up.

the overflow tank needs to be vented to atmosphere. not sure it [the vent] can be on the bottom of the tank unless it exit's the top at some point ?
i can't see that in your picture.
very nice polishing by the way !

TIMING TIMING TIMING IT WILL NEVER RUN COOL AT 28 29 DEGREES OF TIMING TOTAL my 610 cuin hemi will never run cool at 28 degrees itruns the best at the drag strip at 29 but on the street i run 35 degrees

Dump the straight antifreeze, it may have worked before on other stuff that wasn't putting as much heat into the coolant, (maybe blocks with less rust inside too, that weren't .060 over) but its thicker and doesnt dissipate heat the same. In fact I noticed my car runs 10-20 degrees cooler with straight water vs 50/50.

The fan mounting plate, as mentioned, might be an issue.

I would try a stock water pump and water pump housing if you have one and the fans/mounting plate don't make a difference.

More timing will help, some engines really run hot when you disconnect or don't run vacuum advance. I would expect that knocking it back to 28 made your problem worse.

So I moved the shroud back 3/4", bumped the timing up to 34 degrees were I usually keep it and took it for a 16 mile round trip to get gas in the tank. The temp gauge went to 205 degrees. The outside temp was 85 degrees. The first 8 miles it held at 195 running at 55mph, on the return it jumped to 205 cruising at 65 mph, sat in the driveway and let it run for about 3 minutes and the temp stayed steady at 205. Next try a water mix and move the trans cooler a little more out of the way of radiator air flow. The trans cooler has a 2" gap in front of the radiator. Can't run straight water in Michigan, during the winter the water would freeze and crack the block. Seen this many times when guys forgot to drain the block before winter weather. If someone in Michigan has a stock belt driven radiator fan I could borrow I would try that before moving on. I had the same setup on my 64 Plymouth with a 500" wedge and it never went above 180 degrees in traffic. Same water pump and housing, same size pulley set. The only difference is the brand radiator and electric fan on this car. Wedge vs Hemi both with aluminum heads.

I like at least three rows inside the radiator. The more time the coolant had sitting in the radiator the more it cools from one row to the next. One other thing I run a mated Water Pump Housing and Pump. There are a lot of differences between housing and pumps. NHOA did a study at one time and put it in there news letter on all the pumps and housings. I run a 160 high flow quick opening Stat. My set up is completely factory, 26 inch cooper rad, factory E Body completely but I do not run the clutch on the fan just the seven blade fan. I never run anything but a mixture of Anti Freeze and water like Chrysler does. 50/50. The Temp stays around 163 degrees temp taken of the pump. I don't think you want to go to what I have since you have spent money and time on making the cooling look a lot prettier than what I have. I believe you have tried all kinds of thing with the timing it can be a big contributor to a heating problem.

like others have said, ditch the plate holding the fans. I would start there. I tried that once with puller fans and it wasn't a good result. Electric fans can work, just make sure they are high flow like a spal fan. Not the chinese no name ones.