Car getting real hot....

[Dale Davies]

Which I posted because while we are discussing MAPS car and engine, there were comments about how they beleived Chrysler engineers intended the systems to work. After I provided snips of directly from the Chrysler tech literature of the time, one would have thought that would have been pretty good evidence. My post was intended to draw attention to the obvious contradictions between what some people have typed and what is in the books regarding the original systems.

I believe you Mattax, I apprenticed for Auto Mechanic at that time. I got an Interprovincial Red Seal on my mechanic license. I also apprenticed for Heavy Duty mechanic when it covered all areas before they split it up. Now truck and bus are separate from construction equipment. I have worked on everything from Austin Minis and MG Migets to 150 ton rock trucks, drag lines and loaders. This ticket also has an Interprovincial Red Seal. The Red Seal lets me work across Canada except Quebec.
Worked on Detroit Diesels for years. Had one come in that could idle all day or bobtail without overheating. Pick up a trailer and it would overheat pretty quickly. I found a shop rag wadded on the WP impeller. Another mechanic had been working on it 200 miles away and forgot the rag in the lower hose when he put the new radiator in.

 

[Ricks70Duster340]

Had one come in that could idle all day or bobtail without overheating. Pick up a trailer and it would overheat pretty quickly. I found a shop rag wadded on the WP impeller. Another mechanic had been working on it 200 miles away and forgot the rag in the lower hose when he put the new radiator in.

It's often the little things that get us. Thanks for sharing!

 

[Dana67Dart]

but can you someone please tell me why I never, ever, had this problem

Because you changed something in the system. It is that simple, you rebuilt the engine, you changed the WP, I assume you changed the thermostat. Who knows what else might have been changed that made it happen, new temp sender???

The list goes on and on

 

[RustyRatRod]

Apparently some of you guys don't beleive what the Chrysler engineering team wrote..

I'm not sure that's what it is. What they wrote changed over time and some are still latched onto what they said "at first". At least that's my understanding.

 

[Dale Davies]

I'm not sure that's what it is. What they wrote changed over time and some are still latched onto what they said "at first". At least that's my understanding.

New technology is developed, new materials come along. Better metalurgy, better oils and filtration and of course fuel injection have all contributed to enhanced life expectancy of our vehicles. That said, the old engineers were pretty fart smellers for what was known then. The factories have test equipment that only the top race shops may have. They were testing stuff we only get wet dreams over.

 

[Mattax]

I'm not sure that's what it is. What they wrote changed over time and some are still latched onto what they said "at first". At least that's my understanding.

LOL. Yes it always depends on what 'it' is being referred to.

And yes what people hear and repeat could either be comletely erroneous, or something that changed over time. We can just look in the various service manuals etc and see that thermostats were changed, cap pressures changed, overflow recovery tanks added. What was done on an 'open' system without emissions idle settings was different that recovery systems later in the emissions era. blah blah yada yada

 

[RustyRatRod]

LOL. Yes it always depends on what 'it' is being referred to.

And yes what people hear and repeat is could either be comletely erroneous, or something that changed over time. We can just look in the various service manuals etc and see that thermostats were changed, cap pressures changed, overflow recovery tanks added. What was done on an 'open' system without emissions idle settings was different that recovery systems later in the emissions era. blah blah yada yada

I just do what works. This is where I've lived my whole life. It's hot and humid. It's a *****. But out of all the hot rods I've had (over 400) I've never once had an over heating problem but it not for some kind of failure like a hose rupture or water pump failure. I've never just had a "running hot" problem. Never.

 

[IfItsGotWheels]

@yellow rose


That's all..... And I still can't get my guage to slow down and hitting 200 within 10 mins of driving sometimes if I'm in the city, once I get on the highway or express lanes I'm down to 160..
Morale of the story, stay off the streets..

MAPS

I repeat what I said earlier, 200- 210 degrees in stop & go traffic is acceptable, as long as the temperature drops when cruising. If you want better results get rid of the flex-fan & do something about that restrictive shroud.

 

[Mattax]

I just do what works. This is where I've lived my whole life. It's hot and humid. It's a *****. But out of all the hot rods I've had (over 400) I've never once had an over heating problem but it not for some kind of failure like a hose rupture or water pump failure. I've never just had a "running hot" problem. Never.

Funny I haven't either. Not owned nearly that many cars though.
Just so there's no confusion, you're not the guy writing a paragraph that begins with an explanation that Tech said is "a misunderstanding" because some of their competors have systems like that.

 

[RustyRatRod]

I repeat what I said earlier, 200- 210 degrees in stop & go traffic is acceptable, as long as the temperature drops when cruising. If you want better results get rid of the flex-fan & do something about that restrictive shroud.

It is, I agree 100%. Here's where the problem can come in though. In the south, in middle Georgia, this summer weather can and will tax a cooling system to the boiling point.....pun intended. We're fortunate enough to live out in the sticks where it's a 20-25 minute drive at the very least to "anywhere". I prefer to get one running as cool as possible because of the possibility of getting hung up in traffic in either Macon or Milledgeville. Gray is not an issue, since the population there is only around 3000 on paper.....even though probably 10K people are there during the day. There ain't but THREE traffic lights. lol

All that said, the cooler a hot rod runs, the more "space" you have until the cooling system becomes overtaxed and cannot shed heat anymore. ....and it can and will happen to even the best cooling systems under the "right" conditions. If one is running as cool as possible, you have a lot more room before that happens.....IF it ever does.

 

[CFD244]

A/C water pumps were driven faster than non-a/c water pumps.
35% faster in 1968
The faster they are spun, the more liquid flows and the likelyhood for cavitation increases. Those are both minimized with the smaller impeller.
View attachment 1715752743

Ignore the yellow markup. That was for someone else's question.
The big issue with A/C is not the additional load on the engine, which is real, but only a significant load percentagewise at idle rpms.
The big issue with A/C is the heat exchange with the air - the same air that goes through the radiator. Its critical to keep enough volume of air moving at idle and low speeds.

My '71 service manual must have a mis-print? Where it references the the ratio, it specifically states "fan to crank" ratio. That being said, standard cooling is listed at .95:1 ratio (fan smaller than crank equals over-driven), while A/C cooling is listed at 1.31:1 (fan larger than crank equals under-driven). This logic makes no sense, while yours does.

 

[Mattax]

My '71 service manual must have a mis-print? Where it references the the ratio, it specifically states "fan to crank" ratio. That being said, standard cooling is listed at .95:1 ratio (fan smaller than crank equals over-driven), while A/C cooling is listed at 1.31:1 (fan larger than crank equals under-driven). This logic makes no sense, while yours does.

I see where you are coming from and why that could be misleading.
The charts in the earlier manuals like posted here just say ratio under Fan.

@Dana67Dart has previously posted the measurements from his car.
"My 67 273 (no AC) has about 6.125 crank and 6.5 water pump pulley, that is a 0.95:1 ratio (6.125 / 0.95 = 6.47)"

I would do the math this way if calling it Crank to Fan ratio.
6.125" Crank : 6.5" dia Fan and pump
We want the second part to equal 1 so we divide both sides by the diameter 6.5"
0.94 Crank : 1 Fan

Tha makes sense since we know the fan is just slightly underdriving the standard water pump and fan.

In this post, is a photo of a "1970 up" single sheave crank pulley with an outer diameter of 6.5"
And in the next post presumably the matching water pump pulley which looks to be 6.8" O.D.
6.5" dia Crank: 6.8" dia Fan
.95 Crank :1 Fan

So I think that's all right. Its just how you look at the numbers.
A/C pulleys are sometimes more complicated as I've seen some that have different diameter sheaves on one pulley.
But here's a picture of 1970 engine and we can clearly see the fan and pump are driven faster than the crank turns

Photo from this post Need measurments on 1970 340 AC water pump pulley please

This has a bunch of good comparisons and measurements if any one needs
Pulley ID thread

 

[MAPS]

@Col_Steve

Thank you for your thoughts and opinions.
As stated earlier, I listen to everyone or anyone when I'm asking for thoughts and opinions. Not just for myself, even if others are looking into a situation they may have, I give everyone thoughts respect and value their views.
Long story listening, I see that this will be an issue (process) of elimination. Remove A and replace with B. See no change move on to C.
From what I have gathered from most, my "A" & B" for now are Shroud and Fan.... And the Rad Cap is a close "C" Hopefully, it will be resolved soon while taking baby steps in the process.
Can take one huge leap and in the end, I may land in the Lake (L)... Far away from ABC or D....

Lastly, I do not have any issues on the highway (i think you said the reason I'm having ..... On the highway is because of the shroud, fan etc) but I don't have any heating problems then, it's just in the city when I start going bumper to bumper traffic.
Thank you for all the advice.

Regards,

 

[MAPS]

I just wanted to let all those that have told me that I made a mistake with the fan and radiator I have in the car.

I bought the car like this, I did not have anything to do with it, if it were me, no matter the size, quality, looks of the Rad, I would have gone with what the cars came with originally. For one reason or another, almost all the cars I've have had, used their original style heating set-up.
These Russell brand style hoses are not something I ever used for my Rad, hoses etc..

Thank you.

 

[66fyssh]

@MAPS , try this.

Have the car idling in Park with the hood down and hold up a paper towel to the front of the grill.

See if it gets sucked into the grill.

Going down the road you don't even need a fan as the air is rushing through the radiator. It's slow driving and stopped that you need a fan and shroud to pull air through.

 

[yellow rose]

The coolant always expands as it heats, and hot spots in the heads make some steam pockets that also expand the coolant volume. When coolant volume grows to the point in the top tank to where liquid coolant eliminates the 1" headspace it then makes contact with the breather valve on the radiator cap seal whence that valve slaps shut instantly and cooling system pressure is allowed to build instantaneously. Once pressure is at 16-17 psi the steam bubbles in the hot spots collapse due to the 16PSI pressure thus restoring the pure liquid to metal contact necessary for best heat transfer. 50/50 Ethylene glycol @ 16 PSI boils at about 276* which greatly reduces boil overs on parked cars. As to heat exchange in radiators is concerned the faster you can flow the water through the core and the faster you can flow cool air over the core, the more Btu's will be extracted from the fluid. Therefore running the water pump shaft/fan shaft at as high a speed as possible without creating cavitation in the impeller will result in dumping more btu's into the air than any other combination. Back to the OP's problem, That shroud design is the worst I've seen. It is way too close to the core, and has no aerodynamic sweep from mounting edge to fan opening. The fan you have chosen is a very poor performer and should be replaced with a HD clutch driven 5 blade mopar fan. History lesson time: The 69 hemi a-bodies used the same 22 inch 3 core radiator and shroud +5 blade clutch fan as the 340 a/c cars did, and they did not overheat on Woodward Ave. Here are some photos of my 69 cuda 550hp 470ci A/C equipped cooling system. Eddy heads, 11.3:1 CR .033" quench height, 246* @.050" Camshaft. Timing 15*btdc idle, 53* btdc light throttle cruise. Fuel mixture at light cruise is 15.3:1. Original OEM 3 core brass radiator is offset forward on its brackets 3/4 inch to gain room for the clutch fan clearance on the big engine. The 1/2 inch gap between the OEM factory shroud and the top tank is stock and acts as a vent during high speed operation. 5 blade asymmetrical fan, and HD viscous fan drive are OEM replacements. Engine idles @800RPM in gear with A/C on and on our hottest day so far 91* resulted in some extended traffic light temps of 205* otherwise out on the road it runs at the 195 thermostat temp regardless of gear or speed. You have a fine radiator, and a usable water pump...it is your shroud and fan that are letting you down. The shroud is blocking airflow at highway speed, and the tiny bladed fan can't suck enough air at idle. OTOH those are sure nice pulleys! Best Wishes, Steve

View attachment 1715752968

View attachment 1715752970

SOMEONE NEEDS TO MAKE THIS PIST A STICKY. IM SERIOUS. GREAT POST.

 

[yellow rose]

I'm not sure that's what it is. What they wrote changed over time and some are still latched onto what they said "at first". At least that's my understanding.

PUZACTLY. What they wrote in 1969 about oil is absolute nonsense today.

It is 100% BULLSHIT and bad philosophy to keep telling people you have to slow the coolant down for more effective cooling. That is WRONG and I don’t care who writes that it’s not. I never gave a crap what any engineer says until I’ve proven it out. Chrysler was way, WAY out in front on their ignition stuff. Carb tuning too. I have to grab my 73 FSM to remember what it says, but IIRC all the 340’s and 360’s had overdriven pumps.


Now...let’s talk about how this works some more. I am of the opinion that the THERMOSTAT is what SHOULD set the MINIMUM OPERATING TEMPERATURE. who can argue that? I know one guy who will try. Minimum operating temperature is exactly what the thermostat is supposed to do.

Now that we have the thermostat to set the minimum operating temperature, we can talk about why a guy can use a 180 degree thermostat and have a cruise temperature of 190. Or 195. Or higher.

It is exactly because the cooling system can NOT dump enough heat to keep the MOT of the thermostat and the cruise temperature the same. They really should be. So when someone says “I run a really nice high flow 180 degree thermostat and going down the freeway my gauge says 195 and that’s where it should be because that’s not too hot” I say you are wrong. You are better off with a 195 thermostat so the minimum temperature is controlled by the thermostat and not the crap cooling system.

It’s simple really. And it’s pretty dumb to use a 180 or colder thermostat if you don’t want fix your cooling system so the split between MOT and cruise temperature is the same, or damn close to it.

The only ways I know of to make the cooling system more efficient is to make the radiator bigger. Then use two big cores instead of 3 or 4 smaller cores. Get an 8 blade impeller high flow water pump or a Flowkooler so you can move some coolant. Then get a Stewart Components high flow thermostat. There isn’t a better thermostat on the market. Not even close. The least thing you need to do is speed up the water pump. Go as fast as you can find pulleys. And keep the belt on. You can’t get too fast. I don’t believe you can cavitate the pump with any speed you can get from available pulleys. So speed it up.

If you do that, you can easily run a 180 degree thermostat and drive through downtown hell and not go more than 5 degrees over thermostat opening. I think if everything is right, including the tuneup, you can use a 160 thermostat and keep the coolant right there. If you have it all right.

Never, ever slow the pump down unless it’s throwing the belt. Don’t ever use anything but an 8 blade impeller high flow pump or the Flowkooler pump. Don’t cheap out on the thermostat. Quality is quality. Get the biggest radiator you can fit with no more than 2 cores. And the 2 cores should be as big as you can get.

Do that and you won’t mind driving through hell.

 

[yellow rose]

I repeat what I said earlier, 200- 210 degrees in stop & go traffic is acceptable, as long as the temperature drops when cruising. If you want better results get rid of the flex-fan & do something about that restrictive shroud.

That’s only acceptable (at best) of you have at the coolest a 195 degree thermostat. If you get those numbers with a 180 thermostat the cooling system is highly deficient.

 

[yellow rose]

I repeat what I said earlier, 200- 210 degrees in stop & go traffic is acceptable, as long as the temperature drops when cruising. If you want better results get rid of the flex-fan & do something about that restrictive shroud.

No, it’s NOT. You can call it that but it’s not. Nothing need to be that hot. Especially a performance engine.

 

[RustyRatRod]

PUZACTLY. What they wrote in 1969 about oil is absolute nonsense today.

It is 100% BULLSHIT and bad philosophy to keep telling people you have to slow the coolant down for more effective cooling. That is WRONG and I don’t care who writes that it’s not. I never gave a crap what any engineer says until I’ve proven it out. Chrysler was way, WAY out in front on their ignition stuff. Carb tuning too. I have to grab my 73 FSM to remember what it says, but IIRC all the 340’s and 360’s had overdriven pumps.


Now...let’s talk about how this works some more. I am of the opinion that the THERMOSTAT is what SHOULD set the MINIMUM OPERATING TEMPERATURE. who can argue that? I know one guy who will try. Minimum operating temperature is exactly what the thermostat is supposed to do.

Now that we have the thermostat to set the minimum operating temperature, we can talk about why a guy can use a 180 degree thermostat and have a cruise temperature of 190. Or 195. Or higher.

It is exactly because the cooling system can NOT dump enough heat to keep the MOT of the thermostat and the cruise temperature the same. They really should be. So when someone says “I run a really nice high flow 180 degree thermostat and going down the freeway my gauge says 195 and that’s where it should be because that’s not too hot” I say you are wrong. You are better off with a 195 thermostat so the minimum temperature is controlled by the thermostat and not the crap cooling system.

It’s simple really. And it’s pretty dumb to use a 180 or colder thermostat if you don’t want fix your cooling system so the split between MOT and cruise temperature is the same, or damn close to it.

The only ways I know of to make the cooling system more efficient is to make the radiator bigger. Then use two big cores instead of 3 or 4 smaller cores. Get an 8 blade impeller high flow water pump or a Flowkooler so you can move some coolant. Then get a Stewart Components high flow thermostat. There isn’t a better thermostat on the market. Not even close. The least thing you need to do is speed up the water pump. Go as fast as you can find pulleys. And keep the belt on. You can’t get too fast. I don’t believe you can cavitate the pump with any speed you can get from available pulleys. So speed it up.

If you do that, you can easily run a 180 degree thermostat and drive through downtown hell and not go more than 5 degrees over thermostat opening. I think if everything is right, including the tuneup, you can use a 160 thermostat and keep the coolant right there. If you have it all right.

Never, ever slow the pump down unless it’s throwing the belt. Don’t ever use anything but an 8 blade impeller high flow pump or the Flowkooler pump. Don’t cheap out on the thermostat. Quality is quality. Get the biggest radiator you can fit with no more than 2 cores. And the 2 cores should be as big as you can get.

Do that and you won’t mind driving through hell.

Flowkooler makes a high flow pump for the slant 6. It's on my list.

 

[1969383S]

Flowkooler makes a high flow pump for the slant 6. It's on my list.

It should be!

 

[Mattax]

@Yellowrose, your concept about the t-stat setting the minimum temperature is basically correct. But your numbers don't work out if the shop manual is correct, and I think you are wrong to dismiss it. The thermostat openings have a plus minus of 5 degrees to crack open enough to get a feeler gage in. Full open is around 20 degrees hotter - plus minus some. Surely you're not saying those shop manual specs are incorrect.
This is what my post was referring to.
Also when tech goes out of their way to say that the 1968 Chrysler system does not pressurize due to coolant expansion, then someone says that cooling systems pressurize due to liquid expansion; that person either didn't read the explanation, or doesn't believe Chrysler knew how their own system worked.

Now, why run a hotter rather than a cooler engine?
On a low compression street setup I would give two reason:
1. To get rid of the condensate in the engine, especially the oil.
2. To more completely vaporize the gasoline.
Now that second can be argued about. I don't have numbers or test or any of that. But this is what Shrinker was always writing about and I buy it. When we set up relatively low compression situations we need to get enough heat in the chamber so light and medium portion of the fuel vaporizes and distributes evenly before spark.
On some engines this isn't going to apply because the heads, piston and cam are doing the work. So on some engines more heat could hurt. I get that.

 

[69hemibeep]

The thermostat is for minimum operating temp, too cold an engine is bad news. Every water cooled car on the road will run warmer than the stat depending on conditions that doesn't mean the cooling system is inadequate.

 

[Dana67Dart]

That being said, standard cooling is listed at .95:1 ratio (fan smaller than crank equals over-driven), while A/C cooling is listed at 1.31:1 (fan larger than crank equals under-driven). This logic makes no sense, while yours does

IIRC...The water pumps are different, number of vains etc.

 

[ir3333]

here's my 2 cents...and i've been wrong before.
The thermostat sets the maximum temperature and starts to open when that temperature is reached.The temperature will continue to rise about 5 or 10 degrees until coolant from the rad lowers the temperature in the heads and cylinders.The thermostat never fully closes after the initial opening and the temperature will not change from then on.The speed of the coolant must be reduced to a level that keeps it in the rad long enough for the heat to be dissipated by the rad, usually about 30 degrees (Delta T) If your cooling system is not adequate the temperature will rise when conditions become more severe like a stop and go traffic.
The heat exchanger or rad and fan are the only items cooling the engine temperature if all else is working correctly
Monkey around changing flow ,thermostat or other components is like throwing darts and you may end up with a system that works great or a whole pile of grief!