210° @ Cruise and 180° @ Stop? What's Going On?

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DEVIOUSDUSTER

DEVIOUSDUSTER

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Hello A Body Nation

I'm perplexed...

I have a freshly built motor and transmission that is running hotter at cruise than it does in stop & go traffic. What could this mean?

Quick details:
-Newly built 410 stroker (less than 300 miles)
-Newly rebuilt A727 (TransGo-2 Shift Kit)
-New PRC aluminum radiator
-2x 11" Electric Spal Puller Fans (3010040011) - Attached to aluminum shroud and set on individual relays (Fan #1 @ 180° / Fan #2 @ 195°)
-Mopar 8 Blade Mechanical Water Pump (MOPP5249559)
-Dana 60 3.73 Gear

I understand a new motor takes some time to loosen up but this is kind of weird. Usually cars run hot in stop and go situations and not at cruise. 210° isn't out of the norm but I just don't see how it can run that warm at highway speeds (with fresh air pulling more than the fans) as opposed to traffic where the fans do all the work.

You're feedback is appreciated.
(I can give further part details but I'm really just curious about what could be causing this phenomenon)
 
What rpm is it turning when it starts getting hot?
 
Too much vacuum advance? If you are running it try it without. Either way it could be too much timing. There also could be an air flow issue in the grille or core support. The rubber seal on the front of the hood may be missing. Does your shroud have the vent flaps for speed?
 
Needs more water flow.
 
RustyRatRod said:
Needs more water flow.
Click to expand...

Through the radiator, through the water pump or through the thermostat??

Mines does the same thing, OK in town but starts to get hot after I've been on the highway for more than 10 minutes of continues driving over 50 MPH.

Thanks,
Treblig
 
Are you running a thermostat? The system does require some restriction to keep the heads from cavitation.
 
Maybe the gap between the hood and the top of the radiator needs to be sealed better to avoid air from recirculating at speed. Try to seal that gap off with something and see if things improve.
 
if it gets hot in traffic = not enough fan

if it gets hot at cruise speeds = not enough radiator.
 
mguner said:
Too much vacuum advance? If you are running it try it without. Either way it could be too much timing. There also could be an air flow issue in the grille or core support. The rubber seal on the front of the hood may be missing. Does your shroud have the vent flaps for speed?
Click to expand...

No seal on the bottom of the hood. I have an AAR/Stinger fiberglass hood that uses low tension springs and rubber bumpers. Latched with Eddie Motorsports hood pins.

Do you have a picture of what the seal or flaps should look like? Never thought this would be the issue.
 
Between the hood and the fan and shroud setup you could have an aerodynamic issue affecting the flow you need. If there are large closed off sections outside of the fans you should cut out some rectangles or fairly large areas that you can put flaps on. They will suck shut at idle and blow open at speed. The rubber is a flattened V that attaches to the bottom of the hood right above the core support so it fills out and closes the gap at speed. A chin spoiler may also help.
 
mguner said:
Between the hood and the fan and shroud setup you could have an aerodynamic issue affecting the flow you need. If there are large closed off sections outside of the fans you should cut out some rectangles or fairly large areas that you can put flaps on. They will suck shut at idle and blow open at speed. The rubber is a flattened V that attaches to the bottom of the hood right above the core support so it fills out and closes the gap at speed. A chin spoiler may also help.
Click to expand...

Thanks mguner. I understand the logic behind the flaps I'm just having a hard time visualizing what these modifications would look like. I just finished a 5 year rotisserie restoration and don't really want to do too much carving.
 
I found this image of a hood to radiator seal. (Courtesy of FABO) Does everybody run this? I see it's available from a couple vendors but... it's not the most aesthetically pleasing piece. I don't recall seeing this on the last few Dusters I checked out at the local shows.
 

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Of course I run it.

It's what force air through the radiator. Otherwise air just goes around it. Then it add to the pressure behind the radiator reducing the airflow created by the pressure differential.

Does your PRC radiator seal itself all the way around the radiator support. A lot of aftermarket radiators do not. Add closed cell foam to seal that up.

A lot of those "Hot Rod" Spal fan setup just aren't that adequate. They look cool though.

There a guy here on FABO that just added a hood seal and it made a significant difference.
 
Logan said:
Lower radiator hose collapsing at the higher cruse RPM?
Click to expand...

X2. You beat me to it, Logan.

Based on the OP's description this could certainly be happening. Does the lower rad hose have a spring inside to keep it from collpasing?
 
DEVIOUSDUSTER said:
I found this image of a hood to radiator seal. (Courtesy of FABO) Does everybody run this? I see it's available from a couple vendors but... it's not the most aesthetically pleasing piece. I don't recall seeing this on the last few Dusters I checked out at the local shows.
Click to expand...

That is one of the most important pieces of the cooling system.

It keeps the hot engine bay air from being drawn back over the top of the core support and recirculated through the radiator.
 
Put the hood seal on if it's missing for sure. IMO though, that will not make the difference. You are talking about running 30* hotter going down the road at highway speed. Stick your head out the window. That's a LOT of air flow and your head has way less surface area than the front of your car. The air flow is sufficient, IMO. You need more water flow.
 
My money is on the shroud restricting air flow.
I didn't see a pic of it to have that oppinion, but I'll bet ya. :D

Think about it.
all that needed airflow from being under a load trying to pass through 2 eleven inch holes on the hiway?
I don't think so.
 
Never saw the questions answered concerning total timing and Fuel mixture. (Don't overlook them!)

I had the same issue and once the total timing was ironed out my cruise temps dropped off.

Have yet to get a read on the plugs again after the change in timing but they looked way on the lean side prior to recurving the Distributor.
 
Thank you all for the responses. Lots of great suggestions here! I will be purchasing the hood to radiator seal this week. Other items I'll be checking are the spark plugs, timing, fuel mixture and possible collapsing of the lower radiator hose (currently no spring). If no fix after running through these items - will look into creating some additional ventilation around the shroud.(Cutting openings and using flaps)

More than enough to tinker with here and the good news is none of it seems to cost too much coin.

As always - thank you for the help. I'll let you know how things progress.
 
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