Engine Temp increases/decreases with Speed?
#1260149
07/01/12 08:15 AM
07/01/12 08:15 AM
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Joined: Sep 2009
Posts: 1,377
Tennessee
WyleECoyote
OP
pro stock
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OP
pro stock
Joined: Sep 2009
Posts: 1,377
Tennessee
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84 D-350, auto, 4.10's - with a stock 72 440. Engine has been running cool since March when I started driving the truck. Now that the atmosphere temps have raised here in Tennessee and its officially "hot" out - the engine temp goes up and down with my speed.  45mph - 190 55mph - 210 65mpg - 230 There is a 30-degree difference from top of radiator to bottom; 200 top, 170 bottom. Good mix of antifreeze and distilled water. Although the mph/temp readings above are from a cheap aftermarket set of gauges, the heat gun on the thermostat housing and radiator are about 5-degrees less - and for what its worth, the dash dummy gauge just starts to go over the mid-way point when its at 230. Could this be a timing issue that has only reared its head now that its 100-degrees outside?  What say you? Thanks.
Wile E. Coyote
Super Genius, Lover of FCA US LLC Products
*************
68 Road Runner (440 4-spd), 71 Superbee (383 slap), 71 Charger 500 (383 4-spd wA/C 1of 182), 72 Imperial, 74 Charger SE (440 sunroof), 84 D350 Crew-cab Dually (440), 75 D300 Dually Tandem (318 4-speed)
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Re: Engine Temp increases/decreases with Speed?
[Re: bonefish]
#1260152
07/01/12 10:35 AM
07/01/12 10:35 AM
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Joined: Sep 2009
Posts: 1,377
Tennessee
WyleECoyote
OP
pro stock
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OP
pro stock
Joined: Sep 2009
Posts: 1,377
Tennessee
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Quote:
this is going to be interesting. mine does the same thing.does yours start to cool down when you idle?
Yep - sure does. Since its HOT out, it doesn't get back down to 190, but it will certainly drop back from high temps it gets too when driving.
Wile E. Coyote
Super Genius, Lover of FCA US LLC Products
*************
68 Road Runner (440 4-spd), 71 Superbee (383 slap), 71 Charger 500 (383 4-spd wA/C 1of 182), 72 Imperial, 74 Charger SE (440 sunroof), 84 D350 Crew-cab Dually (440), 75 D300 Dually Tandem (318 4-speed)
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Re: Engine Temp increases/decreases with Speed?
[Re: WyleECoyote]
#1260157
07/01/12 11:42 AM
07/01/12 11:42 AM
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Joined: Feb 2003
Posts: 1,665
Milwaukee, WI
Prince_Valiant
top fuel
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top fuel
Joined: Feb 2003
Posts: 1,665
Milwaukee, WI
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I've always wondered if flex fans influenced this too...the idea that as the engine speed increases @ 55-65 range(as we'd expect w/ 4.10's) and the fan flattens, it actually decreases the amount of air flowing past the radiator....
So then the question becomes, are you also running a flex fan?
fwiw, my LRT does as it should...get a touch hotter in traffic idling, but cools down even in these ungodly temps once I get rolling. AL headed .030 over 408 ci small-block w/ 10.5:1 compression, AL radiator, viscous clutched fan....
1979 Dodge Lil' Red Express - 360 rwhp, 13.2 @ 103mph
1968 Coronet: 318, 2.76, 15.2 @ 92mph! (SOLD)
1976 Valiant: 360, 3.90, 12.90 @ 106 (SOLD)
1989 Shelby CSX #500/500
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Re: Engine Temp increases/decreases with Speed?
[Re: fourgearsavoy]
#1260158
07/01/12 11:57 AM
07/01/12 11:57 AM
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Joined: Jan 2007
Posts: 7,664
IN
ahy
master
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master
Joined: Jan 2007
Posts: 7,664
IN
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Quote:
Quote:
Either your radiator is too small or its dirty. Mine stays at 180 until I slow down and have only one of my dual fans on. As soon as I turn on the second fan, right back to 180. I chose electric fans because I race it once in a while and I can cool it down while parked between runs.
 My savoy does the same thing,the small rad is just not cutting it at high-way speeds but runs cool in traffic just idling or cruising.
Sometimes just a small amount of slag will cause high speed overheating issues.My rad is brand new but I just have too much engine to cool with a 19" rad 
Gus 
On the D200 I drove for many years, hot at speed or climbing a hill on the highway told me the radiator was getting plugged. Power flush (hose and compressed air) would help it for a while but the fix was a new or re-cored radiator. NAPA, Autozone or Radiators.com can fix you up. Just make sure you look at the actual specs for the radiator especially core thickness as some aftermarket radiators are really thin.
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Re: Engine Temp increases/decreases with Speed?
[Re: Dan Halen]
#1260159
07/01/12 12:50 PM
07/01/12 12:50 PM
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Joined: Sep 2009
Posts: 1,377
Tennessee
WyleECoyote
OP
pro stock
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OP
pro stock
Joined: Sep 2009
Posts: 1,377
Tennessee
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Quote:
That truck is an '84 which only came with small blocks.
Was the radiator upgraded when the engine was installed?
Even a stock 440 will need more cooling capacity than what was factory
installed in '84. A replacement radiator for a '78 440 truck should
cure your problem, get a max cool while you're at it.
Hmmm..... Yes, I am the culprit that ditched the 360 and transplanted the 440 - but I don't think I thought about the radiator size to cubic inch ratio; I did the swap in 2000 and then put the truck in storage while I went overseas so I don't remember much about it. I will have to go out and measure the darn thing! I'll update ya'll shortly. 
Wile E. Coyote
Super Genius, Lover of FCA US LLC Products
*************
68 Road Runner (440 4-spd), 71 Superbee (383 slap), 71 Charger 500 (383 4-spd wA/C 1of 182), 72 Imperial, 74 Charger SE (440 sunroof), 84 D350 Crew-cab Dually (440), 75 D300 Dually Tandem (318 4-speed)
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Re: Engine Temp increases/decreases with Speed?
[Re: WyleECoyote]
#1260161
07/01/12 01:55 PM
07/01/12 01:55 PM
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Joined: May 2003
Posts: 15,487
Florida
scratchnfotraction
I Live Here
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I Live Here
Joined: May 2003
Posts: 15,487
Florida
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Quote:
Quote:
That truck is an '84 which only came with small blocks.
Was the radiator upgraded when the engine was installed?
Even a stock 440 will need more cooling capacity than what was factory
installed in '84. A replacement radiator for a '78 440 truck should
cure your problem, get a max cool while you're at it.
Hmmm..... Yes, I am the culprit that ditched the 360 and transplanted the 440 - but I don't think I thought about the radiator size to cubic inch ratio; I did the swap in 2000 and then put the truck in storage while I went overseas so I don't remember much about it. I will have to go out and measure the darn thing! I'll update ya'll shortly.
you can swap in a rad from a 86 3/4 ton truck,it is same width but taller with 3-4 rows for max cooling on trucks. 
also check to make sure the lower rad hose is not sucking shut as you increase rpms. this will make temps climb at speed choking off water flow and heat up,then as it opens back up under lower rpms it cools back down.
get a stainless steel welding rod and wrap it into a coil and slip it in the lower hose to keep it from sucking shut.
they stoped putting the spring in the lower hose to save a buck and supposedly the new rubber is stiffer these days and the spring is not needed.
I run a autozone alum/plastic replacement rad in my 88 440 truck and it stays right at 180*,I had the same trouble at first with the lower hose sucking shut. the spring in the hose fixed it.
I also have a new copper/brass rad for the 3/4 ton truck which is a lot taller and 3-row core, but it needs the bigger fan shroud that is made of metal before it goes in.
maybe you should try an acme replacement rad. 
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Re: Engine Temp increases/decreases with Speed?
[Re: scratchnfotraction]
#1260162
07/01/12 02:30 PM
07/01/12 02:30 PM
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Joined: Sep 2007
Posts: 14,889
up yours
Supercuda
About to go away
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About to go away
Joined: Sep 2007
Posts: 14,889
up yours
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temperature problems at idle are generally airflow issues, temperature problems at highway speeds are typically water flow problems.
High flow, turbulent water makes for best cooling. Sounds like maybe the radiator is a cork in the system. But it could be a slipping belt, eroded impeller on the pump, weakly opening thermostat, etc.
They say there are no such thing as a stupid question.
They say there is always the exception that proves the rule.
Don't be the exception.
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Re: Engine Temp increases/decreases with Speed?
[Re: WyleECoyote]
#1260166
07/03/12 01:55 PM
07/03/12 01:55 PM
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Joined: Jan 2003
Posts: 28,067
Irving, TX
feets
Senior Management
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Senior Management
Joined: Jan 2003
Posts: 28,067
Irving, TX
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You measured the radiator inlet and outlet first. That's a good sign.
Did you measure the radiator across the rows? You can often spot a clog when one row is cooler than those on either side.
Do you have any idea what rpm you're running at those speeds? I wonder if your distributor advance is getting pulled too far with higher rpm.
We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind.
- Stu Harmon
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