OVERHEATING

[Dave999]

things not mentioned
wrong cap:- short spring cap in long spring filling spout
loose cap bend over the tangs
system never builds pressure it doesn't necessarily puke but the coolant miraculously disappears.

header tank of radiator below the highest point in the system leaving a big chunk of air in the heads..... you get the same symptoms ????



1) it overheats at a point way past the fan doing anything uesful so not fan
2) it doesn't overeheat on the fan which pulls through such a small amount of air compared with driving at speed, so if the fan can suck enough air to cool at idle and low speed i'd suggest the radiator is potentially ok
3) sounds like under driven pump is in place, this is usually a good thing. if the coolant goes too fast through radiator the coolant doesn't dump any heat. hot radiator hot engine very little heat energy removed. it just recycles it. same happens with no stat in place and you have one in there. all good.
4) evans everlasting radiator goop carries less heat energy per pint than standard blue coolant. it just doesn't degrade in the same way. it comes down to "specific heat capacity of the coolant and its ability to wet the metal surfaces and as far as i can tell evans' isn't any better than standard, and is possibly worse on this front than water and glycol. it behaves differently which could be considerd a benefit but if it was as good as they say military and GM Mopar and Ford would be using it. They may be. but i don't think they are

what i can say is swapping from an OK edelbrock 4bbl set up with what felt like a decent tune and standard advance curve to some spot-on tuned weber carbs with 15 initial and a total of 28* saw my temperature at speed drop by 1/3rd.

I'm now a great believer that many overheat, or in my case just running hotter than expected, issues are timing, tune and distribution related after that experiance.

to me it sounds like the throttle position in the speed range quoted results in a mixture that is marginal and slow burning, and that fire is till rageing as it exhausts down the headers..
Under hood area gets very very hot, very quickly at a specific point in the rev range when you are crusing at speed, and already have max air flow through the radiator.

timing and mixture (content or distribution) related

Plugs mentioned above as well yeah could be... poor flame front, slow burn slow igntion is what i'm talking about. wrong heat range plays havoc.

just my view from my desk at work... perfectly happy to be wrong....

Dave

 

[1969383S]

Pretty early in the year to start seeing a post like this!

50/50 mix? Is your Cruise AF mixture and timing correct or lean?

Pictures of your setup go a long way to helping resolve your issues! Be up front and you will get the help you ask for!

 

[RustyRatRod]

Pretty early in the year to start seeing a post like this!

Not for around here it ain't.

 

[AJ/FormS]

At 3500 your Cruise timing should be at least 50>56 degrees.

I'm gonna say something that is gonna sound crazy;
Once the stat opens, my 367 runs right between 205>207* measured by IR gun, at the hottest place I can find, on or near the stat house. I have never seen her run more nor less, no matter how I drive it.
The reason for that, principally is that the huge 7-blade fan runs on an HD thermostatic clutch, which cycles between almost full slip and full drive, in accordance to what the temp is, of the air that is coming thru the rad.
The waterpump on mine is UNDER-driven in an effort to keep the belt on at 7200 rpm. And yes, she runs an 8-vane pump with an anti-cavitation plate, and all the other stuff that has been mentioned. But the rad is circa 1973, off a 318Dart.
By her trapspeed in the Eighth, she appears to be making 430hp.
But I gotta tell you the whole truth, the first year that she was on the road, I had a heckuva time keeping her cool. Even the second year. And like you, I tried everything.
Finally I took the engine down and honed the holes out another half a thou, and increased the top-ring gaps by IDK, maybe .003>.005. Badaboom, problem solved.
So, IMO, when all else fails, you gotta think about the ring-gaps. If/when you get a lotta heat in the chambers, sooner or later, that heat is gonna find it's way into the pistons and rings. When the rings swell and the ends butt, Bam! you got instant mega-friction, which makes heat.
Happy HotRodding.

BTW, if you are afraid to run a large diameter, hi-attack angle, all steel, 7-blade, clutched fan, because you think it sucks horsepower, fogedabowd it. In the first place, the fan only works at lower speeds, and even in full-on mode, and in Drive I doubt that you'll ever feel it cut in. Secondly at WOT, and over 35mph, the darn thing is mostly freewheeling with the Ram-Air that is slamming thru the rad. It's a non-issue. Once your system is able to over-cool, the T-clutched fan will take care of business, alowing the stat to do it's business.

 

[Inertia]

I've read clutch fans won't spin over 4000 rpm regardless of engine rpm .

 

[Dana67Dart]

I've read clutch fans won't spin over 4000 rpm regardless of engine rpm

There are verious types of clutch fans
Some never go 1:1 or freewheel.


I found this info some time ago.


thermal clutch info

 

[12many]

Must be doing extensive diagnostic work as the OP hasn't replied to any of the many posts here. Hopefully he figures it out.

 

[AJ/FormS]

EDIT;
My T-clutch is out of the Haden catalog, listed for an early 2000s Ford Pick-up. I think it was classified as a HDPlus. Here we are at least 19 years later and it is still working.

 

[Franko]

When it's really hot , shoot the temps of the actual metal fitting top and bottom rad hoses.
You need min 30* drop, 50* would be better

I removed my Glen-Ray re-cored radiator and I'll perform this test when I install a radiator that I am borrowing from a friend.

Did it puke? 220 shouldn't puke with the proper cap and glycol/water mixture.

My radiator overflowed quite a bit with a 16 lb cap, and a 50/50 glycol/water mix, every time I shut her down after it hit 220 degrees.

If your current pump does not have the anti-cavitation plate, and originality is a concern (I assume as you had it rebuilt) I would install a plate on the vanes.

I can't find any info on a cavitation plate or a plate on the vanes. Can anybody explain this and if I can purchase a cavitation plate? Would a water pump cavitate at 3,500 rpm or only at much higher rpm?

First thing that jumps out at me is, your water pump is being under driven.

...while his is under driven by 5 percent it was done on purpose to stock engines.

Would it make sense to purchase and test a slightly smaller water pump pulley to spin the water pump faster, maybe 6" or 6 1/4"? If so, where would be the best place to purchase smaller pulleys?

Is the radiator sealed to the core support to force air into the rad... When you were driving did you hear the fan clutch roaring?

Since the radiator is stock it should have been properly sealed to the core support. I never heard anything from my 18" clutch fan. Plus, I'm under the impression that the fan wouldn't have much effect at 75 mph.

Did it overheat before the radiator was done with a new core

I had my radiator restored at Glen-Ray because of the original overheating issue. Since Bob installed a new 3 row core the fins wouldn't be an issue.

Unless I missed it, nobody has mentioned ign timing. Retarded ign timing will very quickly cause o'heating. Make sure your dist centri weights are moving AND that the vac adv unit is working.
Failure of either/both will cause hot running.

My initial timing is 12 degrees and all in @ 33 degrees @ 1,800 rpm (vacuum advance disconnected) and with the vacuum advance connected all in @50 degrees @ 2,200 rpm.

Spark plugs do three things. They provide spark, keep themselves clean and they PULL HEAT OUT OF THE COMBUSTION CHAMBER.

Start two steps colder.

Shouldn't the current plugs be inspected before going to a different heat range?

My spark plugs are Champion RN12YC. Attached are pictures of their condition. There doesn't seem to be a lean condition. The step-up rods for my stock 1969 340 AVS for a 4 speed, are correct. The original 1969 340 spark plugs are Champion N-9-Y. Could the difference in the spark plug heat range cause this much of an overheating issue?

I started this reply yesterday and left the page open. I didn't responded immediately because I was doing more research. I see there are some more replies didn't show up in what I read and responded to yesterday. I will respond to them in another post.

Thanks to everyone for all the feedback.

 

[RustyRatRod]

"What" exactly are we reading? Idling in the driveway? Full throttle blast? It helps to know.

 

[12many]

For the DIY’r, You cut out a round plate of thin steel and attach it to the vanes, weld it or rivet it etc.. Not something to be bought by itself. A simpler way is to get a Gates 42026P. or similar version. Whether cavitation is an issue or not, I use these anytime I need a new wp.

 

[Frank Mopar]

Your plugs are 3 steps hotter then stock. Thats the wrong way.

Choosing the Right Spark Plug Heat Range

A spark plug's heat range is the degree to which it disperses heat. Find out what the appropriate heat range is for your particular spark plug!

www.championautoparts.com

 

[Dana67Dart]

Would it make sense to purchase and test a slightly smaller water pump pulley to spin the water pump faster, maybe 6" or 6 1/4"? If so, where would be the best place to purchase smaller pulleys

I think you need to figure out the issue before shotgunning any more.

But a wanted ad should get you a pulley.

Make sure to get the right size and depth

 

[Oldmanmopar]

I had my radiator restored at Glen-Ray because of the original overheating issue. Since Bob installed a new 3 row core the fins wouldn't be an issue.

My fins were not the issue. I was talking about the tubes themselves. When pressure testing the radiator to much pressure expanded the tubes, So much that it restricted air flow. It could not be seen by looking at the radiator. But light would not pass through it or air.

The only other thing that could cause overheating that you have not talked about would be severe lean condition caused by to much air and not enough fuel at RPM's. . Or timing retarding to far at RPM's. Or Cam timing?

 

[Inertia]

If the rad can't shed the heat, all that other stuff won't matter .

 

[Bewy]

Fitting colder spark plugs is the worst advice you can get for this engine & shows TOTAL ignorance about spark plug function.
Fitting colder plugs is likely to make the engine run hotter, not cooler. That is because plugs that are two cold cause misfires; the engine now has to work harder & it produces more heat.

 

[Rat Bastid]

things not mentioned
wrong cap:- short spring cap in long spring filling spout
loose cap bend over the tangs
system never builds pressure it doesn't necessarily puke but the coolant miraculously disappears.

header tank of radiator below the highest point in the system leaving a big chunk of air in the heads..... you get the same symptoms ????



1) it overheats at a point way past the fan doing anything uesful so not fan
2) it doesn't overeheat on the fan which pulls through such a small amount of air compared with driving at speed, so if the fan can suck enough air to cool at idle and low speed i'd suggest the radiator is potentially ok
3) sounds like under driven pump is in place, this is usually a good thing. if the coolant goes too fast through radiator the coolant doesn't dump any heat. hot radiator hot engine very little heat energy removed. it just recycles it. same happens with no stat in place and you have one in there. all good.
4) evans everlasting radiator goop carries less heat energy per pint than standard blue coolant. it just doesn't degrade in the same way. it comes down to "specific heat capacity of the coolant and its ability to wet the metal surfaces and as far as i can tell evans' isn't any better than standard, and is possibly worse on this front than water and glycol. it behaves differently which could be considerd a benefit but if it was as good as they say military and GM Mopar and Ford would be using it. They may be. but i don't think they are

what i can say is swapping from an OK edelbrock 4bbl set up with what felt like a decent tune and standard advance curve to some spot-on tuned weber carbs with 15 initial and a total of 28* saw my temperature at speed drop by 1/3rd.

I'm now a great believer that many overheat, or in my case just running hotter than expected, issues are timing, tune and distribution related after that experiance.

to me it sounds like the throttle position in the speed range quoted results in a mixture that is marginal and slow burning, and that fire is till rageing as it exhausts down the headers..
Under hood area gets very very hot, very quickly at a specific point in the rev range when you are crusing at speed, and already have max air flow through the radiator.

timing and mixture (content or distribution) related

Plugs mentioned above as well yeah could be... poor flame front, slow burn slow igntion is what i'm talking about. wrong heat range plays havoc.

just my view from my desk at work... perfectly happy to be wrong....

Dave

Number 4 is dead wrong. You couldn’t be more wrong. I’ve typed out why several times on here so I’m not doing it again.

 

[Rat Bastid]

I removed my Glen-Ray re-cored radiator and I'll perform this test when I install a radiator that I am borrowing from a friend.


My radiator overflowed quite a bit with a 16 lb cap, and a 50/50 glycol/water mix, every time I shut her down after it hit 220 degrees.


I can't find any info on a cavitation plate or a plate on the vanes. Can anybody explain this and if I can purchase a cavitation plate? Would a water pump cavitate at 3,500 rpm or only at much higher rpm?



Would it make sense to purchase and test a slightly smaller water pump pulley to spin the water pump faster, maybe 6" or 6 1/4"? If so, where would be the best place to purchase smaller pulleys?


Since the radiator is stock it should have been properly sealed to the core support. I never heard anything from my 18" clutch fan. Plus, I'm under the impression that the fan wouldn't have much effect at 75 mph.


I had my radiator restored at Glen-Ray because of the original overheating issue. Since Bob installed a new 3 row core the fins wouldn't be an issue.


My initial timing is 12 degrees and all in @ 33 degrees @ 1,800 rpm (vacuum advance disconnected) and with the vacuum advance connected all in @50 degrees @ 2,200 rpm.




My spark plugs are Champion RN12YC. Attached are pictures of their condition. There doesn't seem to be a lean condition. The step-up rods for my stock 1969 340 AVS for a 4 speed, are correct. The original 1969 340 spark plugs are Champion N-9-Y. Could the difference in the spark plug heat range cause this much of an overheating issue?

I started this reply yesterday and left the page open. I didn't responded immediately because I was doing more research. I see there are some more replies didn't show up in what I read and responded to yesterday. I will respond to them in another post.

Thanks to everyone for all the feedback.

View attachment 1716083823

View attachment 1716083824

You are a bit rich at idle and pig rich everywhere else.

 

[Rat Bastid]

Your plugs are 3 steps hotter then stock. Thats the wrong way.

http://[URL]https://www.championaut...choosing-the-right-spark-plug-heat-range.html

[/URL]

They may be 3 steps hotter than what they came with in 1968, but the fuel change required a different heat range of plug.

That 12 is exactly what he should be running. A 9 would be way too cold.

My only suggestion would be to drop the N series plug and start buying the C series plug. It has a 5/8 hex instead of the humongous 13/16 hex which is obsolete IMO.

 

[MOPAROFFICIAL]

When I drove my 1969 Swinger 340, 4 speed, with a 3.55 rear end gear, on the expressway at 75 mph (3,500 rpm), it overheated at 220 degrees, in only 2 miles. Driving on back roads at about 45 mph, the temperature gauge always remained at about 180 degrees.

The 340 was rebuilt a couple of years ago and has 2,800 miles on it. It has the following stock engine parts:
heads, cam, (9.7:1 C/R), intake, AVS carburetor, rebuilt water pump (No. 2863067- 8 vane- for non-AC).I purchased a stock water pump pulley (6 1/2”) and a stock crank pulley (6 1/8”). It also has a fan shroud, clutch fan, 16 lb radiator cap and a 180 degree thermostat.

Then, I had the stock radiator (No. 2949066), re-cored (3 row) by Glen-Ray. It still overheated at 75 mph. Next, I replaced the 180 degree thermostat, with a Robert Shaw/Stewart High-Flow 180 degree thermostat and installed a coil spring in the lower radiator hose, in case it was collapsing at 3,500 rpm. The only improvement was that it took 10 miles to overheat instead of 2 miles.

My engine builder wondered if 3,500 RPM is too high to cruise on the expressway. But it seems that turning 3,500 rpm with a 3.55 would have been normal back in the 60s.

I read the following in FABO: “The other thing to consider is that Mopar and their testing came up with an idea that the eight blade might cavitate at really high RPM”.

Mopar Action (Rick Ehrenberg) stated “the enemy is not heat, but boiling, especially localized steam pockets in the cylinder heads…use a surfactant such as Red Line Water Wetter…”

Muscle Machines (Ask Ray) stated “providing a pulley ratio of at least 1.25:1 relative to crank shaft speed…a RobertShaw balanced -sleeve 160 degree F thermostat and, most important, Evans NPG+ coolant”.

Any thoughts about cavitation, pulley ratio, switching to the six vane AC water pump, Red Line Water Wetter, NPG+ coolant or a 160 degree thermostat?

Thank you for any comments.

Sounds like a shitty radiator cap. Your timing could be either retarded or way advanced... but to get hot at speed...head gasket,detonation or retarded slow/late burn..... but with all else decent...the cap not holding the pressure will do just what you're experiencing.
jmo

 

[Scamp Rhonda]

I think you need to go back to the day that it didn't overheat and work your way forward, troubleshooting what changed to make It overheat. There is a reason why it's doing this. You'll figure it out. Check the simple things first. Don't Over complicate the thought process. Don't change parts because you're guessing. I'd make sure you have good air flow through the radiator before I did anything else. My 2 cents. Good luck!

 

[Frank Mopar]

NGK.com: What is a Spark Plugs Heat Range?

NGK.com specializes in hard to find NGK products.

www.ngk.com

 

[Oldmanmopar]

Here is another issue we had in the past. The Fan and pump on a SBC were for a V belt and we were running a serpentine belt system. They were for reverse direction. The fins in the pump were wrong as were the blades on the fan

 

[Franko]

At 3500 your Cruise timing should be at least 50>56 degrees.

...The reason for that, principally is that the huge 7-blade fan runs on an HD thermostatic clutch, which cycles between almost full slip and full drive, in accordance to what the temp is, of the air that is coming thru the rad.
The waterpump on mine is UNDER-driven in an effort to keep the belt on at 7200 rpm. And yes, she runs an 8-vane pump with an anti-cavitation plate.
But I gotta tell you the whole truth, the first year that she was on the road, I had a heckuva time keeping her cool. Even the second year. And like you, I tried everything.
Finally I took the engine down and honed the holes out another half a thou, and increased the top-ring gaps by IDK, maybe .003>.005. Badaboom, problem solved.
So, IMO, when all else fails, you gotta think about the ring-gaps. If/when you get a lotta heat in the chambers, sooner or later, that heat is gonna find it's way into the pistons and rings. When the rings swell and the ends butt, Bam! you got instant mega-friction, which makes heat.

My timing with the vacuum advance connected is all in @50 degrees @ 2,200 rpm.
I do have the huge 7-blade 18" fan and the thermostatic clutch.
I hope to heck there is nothing wrong with the tolerances in my engine. I had a reputable shop balance and blueprint it.

Is your Cruise AF mixture and timing correct or lean?

Pictures of your setup go a long way to helping resolve your issues!

I don't know what the cruising A/F ratio is. I do have the stock AVS step-up rods (No. 16546- .065" x .063 x .055). I don't think it will help, but attached is a picture of my engine before I removed the radiator and the water pump.

"What" exactly are we reading? Idling in the driveway? Full throttle blast? It helps to know.

All of the above, including quite a while at high idle to change the oil. The plugs probably have 1,000 miles since I cleaned them. I also went up one size on the secondary jets, from the stock .095 to .098. I read that "if the firing end of is spark plug is brown or light gray, the condition can be judged to be good and the spark plug is functioning optimally." My plugs' firing end appear to be light gray.

A simpler way is to get a Gates 42026P. or similar version. Whether cavitation is an issue or not, I use these anytime I need a new wp.

That particular Gates Water Pump has the lower radiator hose outlet on the passenger side for 70 and up. The 69 Gates Water Pump has the 8 vane instead of that impellor shown in the 12many Post. Is that impellor more efficient and better at not cavitating? I'd say that fabricating and welding a cavitation plate seems to be over my head.

I think you need to go back to the day that it didn't overheat and work your way forward, troubleshooting what changed to make It overheat. There is a reason why it's doing this. You'll figure it out. Check the simple things first. Don't Over complicate the thought process. Don't change parts because you're guessing. I'd make sure you have good air flow through the radiator before I did anything else. My 2 cents. Good luck!

This is excellent advice. Regrettable, I never drove the Swinger on the expressway before I had the current 340 rebuilt, because I too many problems with the prior 340 block that was in the car when I purchased it. I eventually figured out that the timing gear was one or two teeth off.
......
My radiator cap is a relatively new stock 16 pound cap from Mancini Racing.

 

[Dave999]

Number 4 is dead wrong. You couldn’t be more wrong. I’ve typed out why several times on here so I’m not doing it again.

Thats fine I've read the advertising and the arguements for and against. some of it makes for compelling reading and some of it is the usual Ad. Man BS.
Just gotta chose which narrative you are swayed by... then try and find some solid science to back it up... and thats where the problems start, finding anything truely indpendent to back up or contradict the claims is nigh on impossible.

i can't find any good science to suggest its better and I can't find any good science to show its worse.

so it comes down to cost, availability and convienience. the first two are the killer for me.

Dave