heating issues when idling 340 73 duster

[woody30]

I have a 73 duster with a 340 in it and going down the road it will run 160 all day but when you stop, it warms right up. Climbs to 210 after about 10-12 min. This is after buying a 1863216 fan with a clutch on it after running a reg 6 blade fan on it to start. I have a universal fan shroud on it now. Didn't have a shroud to start. Warmed up a lot faster before i bought the 216 fan and put the shroud on. Within a couple of minutes it would get to 200+. Any ideas of what else to do. I know it's not terrible now but I'd like it to be cooler at idle. I don't know what it has for a thermostat or if it even has one in it.

 

[4spdragtop]

Hey Stephen good to see you posting. I had heating issues and changed the thermostat. Problem solved, hope yours is as easy a fix.

 

[krazykuda]

Add baffles to the fan and shroud to direct the air through the radiator and not let it get around the radiator...

 

[Kendog 170]

I don't know what you have for a radiator . Look inside and see if your passages are blocked up. But mine ran warm like that for a year until I changed the New T-stat with another New t-stat and problem solved. Hope thats it. In the meantime all the other improvements are a definite plus. T-stat may be frozen 1/2 open.

 

[Plymouth 65]

What pump you running? I recommend a high flow type pump. I also run a high flow 180 degree t-stat. 65'

 

[toolmanmike]

Like 4speed mentioned above, thermostat is often overlooked. Send extra $ and get a good one, test it in a pan of water on your stove with a candy thermometer just to make sure it works before you install it. 180° is what you need. Test or replace the cap. My swinger would act the same as your car. I would drive to a out of town car show and puke coolant out while backing into my car show stall. Not cool. A new cap fixed that issue. The system needs pressure to raise the boiling point past 212°.

 

[Ccas]

All of the suggestions could solve your problem but it's clear you have an air flow issue. That fan is not pulling enough air through the radiator. I'd like to see the design of the shroud.
In the mean time, take a look at the following;
1. is there any obstructions in front of the radiator that prevent the fan from pulling the air through?
2. Does the shroud cover the entire core?
3. Is the shroud sealed to the radiator around the perimeters? That will create a suction affect and increase cfm.
4. is your WP pulley the same or smaller than your Crank pulley? You want your WP pulley to have the maximum RPM's.
5. Tell us more about the radiator. ie; core thickness and amount of tubes.

 

[Kendog 170]

Also 1/2 the fan blade needs to be in the shroud and other half out for proper flow.

 

[AJ/FormS]

You didn't say anything about any mods done to your 1973 lo-compression 340, but you also didn't say it is stock.
As others have said, you have an air flow problem, or a waterflow problem.
Or you are running retarded timing.
I would build the cooling system up to overkill, and once it's working properly, then you can start cutting corners.
So do all the things already mentioned.And I would add;
1) do a compression test to make sure none are blowing into the cooling system
2) get your D recurved to 20* in the D and set Idle timing to 14*, and the all-in (no v-can) to come in no sooner than 3400.
3) If that clutch is viscous only, I highly recommend to get rid of it. Overkill is a large diameter , hi-efficiency,all-steel,direct-drive, 7-blade fan, stuck into a close fitting shroud, half in, as mentioned. Second best is to put a Thermostatic clutch on it.
4) If you are still running a heater, let it be your bypass, and restrict the crap out of the other one. If not running a heater,install a hi-flow stat , and let a lil bit of bypass thru.
You absolutely need an anti-cavitation plate on your pump vanes.
5) If your carb is sucking hot under-hood air, at idle and stopped; that would be operating like a runaway nuclear reactor.
6) You don't need a million-dollar radiator. Once everything else is working right, the rad just needs to be clean inside. Mine is a ancient 1973, out of an air-conditioned 318 Dart.

Once you get it working, I would bring the minimum coolant temp up closer to 190, or more.
Happy HotRodding

 

[Syleng1]

Also 1/2 the fan blade needs to be in the shroud and other half out for proper flow.

This makes no sense- the fan is pulling air thru the radiator. Unless the shroud is day 20” in diameter and the fan is a lot smaller like 16” in diameter. The shroud prevents the fan from sucking air off the tips of the blades - an easier path than thru the radiator. The shroud should be close to the fan but having it sticking out does nothing.

 

[Kendog 170]

I posted an article about fan blade too far into the shroud I had read but can't find it now. Too far in and some air gets pushed back to the radiator. If I find it I'll repost it. Half in and out pulls air better.

 

[Kendog 170]

Found something similar.

https://www.flex-a-lite.com/blog/th...he side of,not efficiently pulling it through.

 

[Ccas]

This makes no sense- the fan is pulling air thru the radiator. Unless the shroud is day 20” in diameter and the fan is a lot smaller like 16” in diameter. The shroud prevents the fan from sucking air off the tips of the blades - an easier path than thru the radiator. The shroud should be close to the fan but having it sticking out does nothing.

the point of the recommendation is that it's a fact that if the fan is too far inside the shroud or too far outside the shroud, the efficiency plummets.
Most factory OEM fan/shroud combinations from the 60's are, give or take, are about even with the lip of the shroud opening.

 

[Mattax]

I'll add this.
160 F is cold for normal operation. If accurate it means the oil (which tracks similar to coolant temps during normal driving) probably isn't into its operating temperature range. Downside of cold oil temps is moisture isn't boiled out and the viscosity is higher than it should be for best flow.
210 F is not fine as long as it doesn't continue to climb.

The differences at idle vs while driving have already been covered. So it does not seem to be due low pressure (bad cap etc) but probably idle air flow or less likely, pulley and pump ratio.
Last possibility, and one that has not been mentioned, is timing. On CAP and CAS era cars the initial timing was reduced compared to earlier engines. This was done to continue the combustion further down the cylinder. Doing so made a more complete burn and put more heat into the cylinder walls - which helped the subsequent burn. Other things were done to somewhat offset the various drawbacks of late timing at idle. No idea what is on your car now much less what it began life with. But its something to keep in mind.

If there are no emmissions (other than PCV and fuel vapor capture) a 340 should idle nicely around 650 rpm at 10 to 14* BTC.
With early emissions it was more common to see 700 rpm (or more!) at 0 to 5* with a real fast advance above idle speed.

 

[woody30]

Thanks for all the suggestions guys, haven't been back on because wife had a tumor taken off her petuitary gland and then developed blood clots in her lungs. She's doing well now. My biggest problem with the car is is i have no idea what has been done to the motor. It was "rebuilt" by the person before the one i bought the car from. One thing I do know is it is over cammed like most. Sounds nasty at idle but is doggy on low end even with 3:91 gears but really comes to life around 2500-300 rpm. The other thing is I don't even know if it has a thermostat in it (i know, that's easy enough to check but have been preoccupied lately). Probably my first things to do are check thermostat and timing and see where it goes from there. Thanks again for all the suggestions.

 

[72bluNblu]

I'll add this.
160 F is cold for normal operation. If accurate it means the oil (which tracks similar to coolant temps during normal driving) probably isn't into its operating temperature range. Downside of cold oil temps is moisture isn't boiled out and the viscosity is higher than it should be for best flow.
210 F is not fine as long as it doesn't continue to climb.

The differences at idle vs while driving have already been covered. So it does not seem to be due low pressure (bad cap etc) but probably idle air flow or less likely, pulley and pump ratio.
Last possibility, and one that has not been mentioned, is timing. On CAP and CAS era cars the initial timing was reduced compared to earlier engines. This was done to continue the combustion further down the cylinder. Doing so made a more complete burn and put more heat into the cylinder walls - which helped the subsequent burn. Other things were done to somewhat offset the various drawbacks of late timing at idle. No idea what is on your car now much less what it began life with. But its something to keep in mind.

If there are no emmissions (other than PCV and fuel vapor capture) a 340 should idle nicely around 650 rpm at 10 to 14* BTC.
With early emissions it was more common to see 700 rpm (or more!) at 0 to 5* with a real fast advance above idle speed.

Absolutely!!!

160* F is cold.

210* F is not dangerously hot (my 340 is a lot happier at 210*F than it is at 160! )

Climbing temps at idle, if it’s a cooling problem, is usually a fan cfm problem. Or a pulley ratio problem (pulley ratio sets the fan speed too!). But yeah, given that the issue is not that extreme, it could even be timing and tuning. A few minor inefficiencies could easily cover what’s being described.

 

[Demonic]

the point of the recommendation is that it's a fact that if the fan is too far inside the shroud or too far outside the shroud, the efficiency plummets.

^ This. It's easy to prove on electrically driven fans in a shroud, like your outdoor fan in your AC condensing unit for your house. When the fan is halfway in the shroud, minimizing the gap, the amp draw will be higher = fan is doing more work. Look at the fan position on original or restored cars.

Low speed cooling issues are usually airflow, with a semi-fouled radiator second. A rad that is "plated out" with scale or rust doesn't flow well at low water pump speeds. As the rpm reach cruise, the differential pressure increases and the flow improves. The real high flow 'stats made a world of difference in my 383. Look for an opening of about 1 7/16" diameter.

 

[AJ/FormS]

I run my 360 at 205 to 207, and it goes like a scalded cat. But, my cooling system is rock steady at 205/207.

 

[72bluNblu]

I run my 360 at 205 to 207, and it goes like a scalded cat. But, my cooling system is rock steady at 205/207.

Totally agree. My electric fans are set to keep my 340 between 200 and 210.

I mean, the original thermostats opened at 195. Obviously modified engines are gonna be a little different, but water under pressure like it is in the cooling system doesn’t boil at 212. Even with only a 7 psi cap you’re talking about boiling at around 230* F. With a 16 psi cap like I run it’s more like 250* F.

 

[toolmanmike]

Totally agree. My electric fans are set to keep my 340 between 200 and 210.

I mean, the original thermostats opened at 195. Obviously modified engines are gonna be a little different, but water under pressure like it is in the cooling system doesn’t boil at 212. Even with only a 7 psi cap you’re talking about boiling at around 230* F. With a 16 psi cap like I run it’s more like 250* F.

Cooling system pressure increases the boiling point 3° per pound of pressure. 15# cap will get you 45° increase.

 

[72bluNblu]

Cooling system pressure increases the boiling point 3° per pound of pressure. 15# cap will get you 45° increase.

That's just an estimate bud. The actual relationship is not linear. I used an engineering calculator that uses the actual formula.

It doesn't have to be that exact anyway. Antifreeze changes the boiling temperature (usually lowers it), stuff like "water wetter" can raise it, and there's always the fact that you can get localized boiling at say, the jackets in the heads because the temperature is not perfectly homogenous throughout the whole system.

The point was simply that 212 isn’t a problem because we’re not boiling water on a stove, it’s under pressure.

 

[toolmanmike]

That's just an estimate bud. The actual relationship is not linear. I used an engineering calculator that uses the actual formula.

View attachment 1715558044

It doesn't have to be that exact anyway. Antifreeze changes the boiling temperature (usually lowers it), stuff like "water wetter" can raise it, and there's always the fact that you can get localized boiling at say, the jackets in the heads because the temperature is not perfectly homogenous throughout the whole system.

The point was simply that 212 isn’t a problem because we’re not boiling water on a stove, it’s under pressure.

LMFAO. According to that chart a 15# system would boil at around 195° c or 383° f. I don't think so Tim!

 

[toolmanmike]

And you do need to take elevation into account. It makes a bit of difference. I am at 880' above sea level. Water boils at about 204°

 

[72bluNblu]

LMFAO. According to that chart a 15# system would boil at around 195° c or 383° f. I don't think so Tim!

It's in Pascals buddy, it's not a chart for radiator PSI.

The point is, it's not a linear curve so 3° per psi is just a very basic estimate. My numbers are accurate.

And you do need to take elevation into account. It makes a bit of difference. I am at 880' above sea level. Water boils at about 204°

Not in a pressurized system it doesn't. Boiling water in a pot, yeah sure. Not inside a radiator.

 

[toolmanmike]

It's in Pascals buddy, it's not a chart for radiator PSI.

That makes more sense.

The point is, it's not a linear curve so 3° per psi is just a very basic estimate. My numbers are accurate.

I can see where it is not linear. I didn't state that 3°/lb. was exact under all conditions.

Not in a pressurized system it doesn't. Boiling water in a pot, yeah sure. Not inside a radiator.

That's apples to oranges the way you state it.
Boiling water in a pressure cooker is the same as a radiator under pressure and elevation dependent. As is water in a pot or a radiator with no cap on.
This is all very interesting. Back to chemistry class.