Overheating 484 Hemi - Need Ideas
#2924077
05/18/21 06:33 PM
05/18/21 06:33 PM
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Joined: Feb 2005
Posts: 957 MI, Lapeer
maximus
OP
super stock
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OP
super stock
Joined: Feb 2005
Posts: 957
MI, Lapeer
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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.
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Re: Overheating 484 Hemi - Need Ideas
[Re: rickraw]
#2924108
05/18/21 07:42 PM
05/18/21 07:42 PM
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Joined: Jun 2008
Posts: 3,916 usa
lewtot184
master
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master
Joined: Jun 2008
Posts: 3,916
usa
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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.
Last edited by lewtot184; 05/18/21 07:44 PM.
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Re: Overheating 484 Hemi - Need Ideas
[Re: lewtot184]
#2924111
05/18/21 07:54 PM
05/18/21 07:54 PM
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Joined: Feb 2005
Posts: 957 MI, Lapeer
maximus
OP
super stock
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OP
super stock
Joined: Feb 2005
Posts: 957
MI, Lapeer
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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?
Last edited by maximus; 05/18/21 08:15 PM.
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Re: Overheating 484 Hemi - Need Ideas
[Re: maximus]
#2924119
05/18/21 08:20 PM
05/18/21 08:20 PM
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Joined: Jan 2003
Posts: 12,284 Benton, IL.
DaveRS23
Special needs idiot
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Special needs idiot
Joined: Jan 2003
Posts: 12,284
Benton, IL.
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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?
Master, again and still
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Re: Overheating 484 Hemi - Need Ideas
[Re: maximus]
#2924144
05/18/21 09:22 PM
05/18/21 09:22 PM
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Joined: May 2016
Posts: 630 Ct
Wirenut
mopar
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mopar
Joined: May 2016
Posts: 630
Ct
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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?
Last edited by Wirenut; 05/18/21 09:23 PM.
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Re: Overheating 484 Hemi - Need Ideas
[Re: gsmopar]
#2924151
05/18/21 09:41 PM
05/18/21 09:41 PM
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Joined: May 2004
Posts: 12,418 Taxes & Virus's R-US, NY
Dragula
I Live Here
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I Live Here
Joined: May 2004
Posts: 12,418
Taxes & Virus's R-US, NY
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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*
Last edited by Dragula; 05/18/21 09:43 PM.
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Re: Overheating 484 Hemi - Need Ideas
[Re: Moparteacher]
#2924187
05/19/21 12:00 AM
05/19/21 12:00 AM
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Joined: Jan 2003
Posts: 7,498 Minnesota
Hemi_Joel
master
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master
Joined: Jan 2003
Posts: 7,498
Minnesota
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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.
[img]http://i.imgur.com/boeexFms.jpg[/img]31 Plymouth Coupe, 392 Hemi, T56 magnum RS23J71 RS27J77 RP23J71 RO23J71 WM21J8A I don't regret the things I've done. I only regret the things I didn't do. "Wise men talk because they have something to say; fools because they have to say something. ~ Plato"
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Re: Overheating 484 Hemi - Need Ideas
[Re: Hemi_Joel]
#2924201
05/19/21 02:28 AM
05/19/21 02:28 AM
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Joined: Jan 2003
Posts: 27,480 So Cal
autoxcuda
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 27,480
So Cal
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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.
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Re: Overheating 484 Hemi - Need Ideas
[Re: FastmOp]
#2924251
05/19/21 08:55 AM
05/19/21 08:55 AM
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Joined: Dec 2004
Posts: 2,368 Wheatfield, NY
Cuda340
top fuel
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top fuel
Joined: Dec 2004
Posts: 2,368
Wheatfield, NY
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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.
Last edited by Cuda340; 05/19/21 08:56 AM.
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Re: Overheating 484 Hemi - Need Ideas
[Re: Cuda340]
#2924255
05/19/21 09:01 AM
05/19/21 09:01 AM
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Joined: Feb 2004
Posts: 34,952 S.E. South Dakota !
bigdad
Still Posting A Lot
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Still Posting A Lot
Joined: Feb 2004
Posts: 34,952
S.E. South Dakota !
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I had this same issue same basic set up you have , tried everything --ended up being a flubbed up distributor
The lips of fools bring them strife, and their mouths invite a beating.Proverbs 18:6
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