1970 300 w/440 running at 220 normal? Is 225 OK stopped in traffic?

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When I got it from the junkyard 20yrs ago, one of the many first things I did was add a temp gauge. It would get up to 240 when it was about 85 degrees with A/C off. So I had the radiator recored, replaced the water pump, did a back flush on the system, and changed the thermostat and hoses. There was a bunch of crap that came out of it. After that, it ran around 235 which was disappointing. So I just didn't drive it more than 10 miles when it was above 85 degrees....Solved.

Since then, I changed out fan clutch, sealed the fan shroud, replaced the ratty old rubber mat under the car so air would be directed to the radiator, did another back flush, replaced with 50% distilled water, 50% prestone, replaced the radiator spring cap and checked the cowl to see if there was anything blocking the exit air flow. It would get up to 230....which again was disappointing.

A couple months ago, I added a 10" electric fan, but noticed about half the airflow doesn't make it past the A/C condenser, however I notice temps don't go up when stopped in traffic. I also tried that expensive ceramic coating paint for exhaust manifolds to lower underhood temps.....worked a little, I guess? Ran at 225.

Last week, I tried that Super Coolant which dropped it by only 5 degrees. Now it runs at 220.

Anyone have any better ideas? Is there a larger radiator I can put in this car without cutting it up? Is 220 too hot when its only 85 degrees outside with A/C off....or am I just being a wimpy guy?

Thanks,

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413

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That is too hot for me. I had a similar situation where I went through everything in the cooling system, and nothing cured it. I found the correct numbered carb and put it on the car runs 185 now, never anymore heating up or boiling over. That was the only change. Lean A/F mix. But the car ran fine, no surging, good power. Was also a 1970 440
HP

what thermostat do you have?
 

HWYCRZR

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If you are truly up into the 230’s I would expect it would cause your radiator cap to vent and spit coolant

I was wrong a 16psi cap should give you up to 268 degrees F before boiling.
 

413

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He has an aftermarket temp gauge on it. First sentence.
 

fury fan

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The OP did lots of repairs and saw some improvements, yet still seems to read high. What if that temp gauge has been faulty all these years?
I would spend some time with an IR thermometer and get a 2nd opinion.

Also - we need a little more info about when it gets hot.
How long does it take it to get hot?
What are the conditions: When idling in traffic for 10 min, or out on the highway?
Or does it do a slow creep upward that it never recovers from?

FWIW - your condenser seems to have some mushed spots that will block airflow.
Do you have an 18" 7-blade fan? Looks like might be 7-blade, but confirm that for us.
 

saforwardlook

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Your top tank indicates the radiator in your car is an aftermarket one and those typically are manufactured for low price - and that means minimum fin density in the cores. These cars even from the factory had poor cooling capability in an effort to save money, so in high temperatures , they run too hot.

I typically use original radiator top tanks but install high fin density "high efficiency" cores to help keep these cars cool in hotter weather conditions, and especially in traffic with the a/c on. High fin density 26" cores typically run about $600 these days but doing anything else just won't cut it. Also, make sure your fluid fan drive is working well and not too loose viscosity wise. Under normal conditions even up to 100F degrees outside under steady state conditions such as on highways, the coolant should not go above about 190F with a stock 180F thermostat and about 215F in stop and go traffic with the a/c on.

This is not someplace where saving money will ever take care of the problem.
 
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AZ - I have an Infared thermometer and never thought of that. I'll give it a try because the aftermarket temp gauge is one of those cheap chinese ones. Maybe its off.

413 - Sounds like the carb might be the problem, but I really hope not. When I got the car 20 yrs ago, the old holley was trash, so I didn't even drive it. I changed to a Thermoquad and its better in everyway (better fuel mileage, no vapor lock etc) than the old Holley. Its never boiled over on me, even in the overflow container.

I also had a hell a time timing this thing. 15yrs ago, I used a timing gun, but the car felt really lazy with low power, high tailpipe emissions, and hard to start, so I bought a Petronix kit and new vacuum advance, but no change. So I took it to a good shop and a mechanic timed it, but no change.

So I played with the timing using my ears and found a sweet spot where the engine seemed calm and happy, power is high, cleaner tailpipe, while still able to start easily. Although I can't use 89 octane, there's a little knocking. I've used 91 and haven't had a knocking problem. Engine runs and idles great for 150,000 miles.

Another weird thing is the "sweet spot" seemed to be only a millimeter wide. Why is the distributor this sensitive??? (Even tightening the distributor bolt down would throw the timing off, so it took forever to time it). If I change the old original distributor (which has Petronix) to a new HEI one, will it help with the overheating???

It takes about 20 minutes to get to 220 and only when its over 85F in traffic and on highway, otherwise its runs around 215. When in the 70's, car tops off at 210. When 60's, it doesn't get over 200, usually runs around 195, so I think its very weather sensitive.
 
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Hey SA - Maybe that will really help. Where do I get one of those radiators? How do I check the fan fluid for viscosity? (Its a new one from last year)

Fury - Yes, its a 7 blade fan.
 
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I'm running a 185 or 195 thermostat, I forgot what I put in there. I heard 440's with a 160 thermostat might help lower heat. Does this make sense?
 

413

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I’d run a 160 and see if it changes.

Those factory holleys are a problem, good swap to a thermoquad.

was that radiator in the car when you got it? Sometimes the blocks are full of sand, sediment and muck when you take out the core plugs. Have you ever had any out? I had and A100 318 with a leaky plug, the block was full above the core plugs, ran so cool after cleaning it all out, was one of the very few easy things on the van.

Can you buy ethanol free gasoline where you live? The ethanol leans the mix somewhat. It may be worth a try, but you have to get it near empty.


retarded timing can cause overheating. That’s the cam timing also when the chain gets loose. Have you ever checked or replaced the chain? Maybe that’s why the ignition timing is so touchy, because the valves are late.
 
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PH27L7

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One thing you can do that costs nothing is to verify the thermostat opens fully at proper temperature in a pot on your stove. The quality of currently available aftermarket thermostats is marginal in my experience. I had one (name brand labeled as high flow) that would only open about 1/8" which resulted in symptoms similar to yours. Some were inaccurate as far as actual opening temperature.
 

3175375

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One thing you can do that costs nothing is to verify the thermostat opens fully at proper temperature in a pot on your stove. The quality of currently available aftermarket thermostats is marginal in my experience. I had one (name brand labeled as high flow) that would only open about 1/8" which resulted in symptoms similar to yours. Some were inaccurate as far as actual opening temperature.
Use a candy thermometer when you check the thermostat in a pot of water on the stove.
 

Ripinator

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When I got it from the junkyard 20yrs ago, one of the many first things I did was add a temp gauge. It would get up to 240 when it was about 85 degrees with A/C off. So I had the radiator recored, replaced the water pump, did a back flush on the system, and changed the thermostat and hoses. There was a bunch of crap that came out of it. After that, it ran around 235 which was disappointing. So I just didn't drive it more than 10 miles when it was above 85 degrees....Solved.

Since then, I changed out fan clutch, sealed the fan shroud, replaced the ratty old rubber mat under the car so air would be directed to the radiator, did another back flush, replaced with 50% distilled water, 50% prestone, replaced the radiator spring cap and checked the cowl to see if there was anything blocking the exit air flow. It would get up to 230....which again was disappointing.

A couple months ago, I added a 10" electric fan, but noticed about half the airflow doesn't make it past the A/C condenser, however I notice temps don't go up when stopped in traffic. I also tried that expensive ceramic coating paint for exhaust manifolds to lower underhood temps.....worked a little, I guess? Ran at 225.

Last week, I tried that Super Coolant which dropped it by only 5 degrees. Now it runs at 220.

Anyone have any better ideas? Is there a larger radiator I can put in this car without cutting it up? Is 220 too hot when its only 85 degrees outside with A/C off....or am I just being a wimpy guy?

Thanks,

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If your aftermarket temp gauge turns out to be accurate, I strongly suspect the coolant passages in your engine block are full of crud. Since you previously flushed out a lot of debris from the cooling system, I think that is likely the problem. As someone else suggested, I would pop the freeze plugs and get in there with a screwdriver or other suitable tool and dig out and flush out all the crud you can. After all that, I bet installation of a 180 degree thermostat and fresh coolant will result in a much cooler running engine.
 

fury fan

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My agreements with some of the comments above. I would look at these things, in the order of cheapest/easiest:

+1 on suspecting timing chain needs review, due to fussiness of ign timing adjustment. That is easy to verify by rotating the engine via the crankshaft bolt and seeing how quickly the distributor rotor responds. (rotate both directions, and only need to rotate enough to take up the slack) The original chainset would've had a nylon-coated cam gear, and there's very little chance it has lasted 150k. But the 2nd chain could've been a cheap one that has also gotten worn, esp due to working against the stiffer valvesprings of a TNT. (I presume that's what you have)

+1 on boil-checking the T-stat. If you have any others laying around, or if you buy a new one, boil them all to see how they compare. (make sure to mark your current one, as you are looking for comparison data)

+1 on that being an aftermarket radiator, I have one like that in my white 68 Fury (Spectra brand?) and the 440 runs hot in traffic. Not as bad as yours, but I don't have an AC condenser blocking airflow.

Non-scientific radiator test - Test your radiator by seeing if it can flow a garden hose without backing up out of the neck (remove the lower radiator hose and flow it empty). Years ago I heard that was a good rule of thumb. If so, *then* plug a rag in the lower radiator outlet and fill the radiator, and see if MORE volume gushes out when you remove the rag. If it can do both, then stopwatch the time for the hose to fill a 5-gal bucket and you have the lower-range flowrate for your radiator.

Glen Ray is a very reputable vendor for new/recores for our cars. I also recently read some good reviews on FBBO of this vendor's products, if you can do the installation yourself and are willing to take a gamble it would save a bunch of $$$. (you'll need to find the right configuration for your car, this link isn't it.)
1966-1972 Mopar B & E Body Aluminum 26" Radiator Road Runner Challenger Cuda | eBay

Comb-out and wash that condenser's fins to minimize the airflow blockage.

FWIW - elec fans like that help in traffic but block airflow when not in use.

+1 on block crud, esp for a 150k engine. You'll be surprised what comes out. That stuff does 2 things - it reduces coolant capacity a little, and it reduces heat-transfer surface area. Although, the bottom of the block is the coolest location.
 

saforwardlook

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I concur with @fury fan suggestions and I was also going to suggest getting a high efficiency radiator core with an original top tank for correct appearance and maximum cooling from GlenRay. Not cheap but worth it and their high efficiency cores do not use the tiny tubes that many high efficiency cores do have that also tend to plug up more easily with a lot of rust sediment lodged in the engine block and the rest of the cooling system. Much of the time, that sediment fills the bottom of the radiators and requires rodding the radiator out (backflushing usually won't do the job very well) to get rid of it but if the engine is laden with a lot of that sediment, it will keep happening.

I too would pull all the freeze plugs and scoop out all the sediment you can access and flush the rest with a good cleaner (and leave the heater core out of the loop if the cleaner can affect the brass in the core if not thoroughly flushed well) but you might have to pull the engine to really do this well.

I see no reason why a lower thermostat opening temperature would affect the cooling capability of the system when it reaches equilibrium, maybe just delay it for a few minutes.

How many miles on your engine? Since you say it is sluggish, it seems to have some timing issues and given the cooling system may well be full of sludge, it might be time for a rebuild. When I rebuild my engines, I also have them acid dipped to remove all the built up crud over the years completely (not just hot tank them - it isn't enough). Acid dipping the block is an extra $500 for me and you might have to search to find a facility that can legally do this anymore but they are out there since I can find one even in California. The block will then look like a new casting and completely free of rust - and thereafter use a good antifreeze and keep it fresh to prevent the problem in the first place.

I also use a Comp Cam with good low end torque to give a little added low end grunt for these 440 engines that really makes a difference in how they feel off the line while not giving up the smooth idle.

If the engine does have high miles and a lot of crud in it, I would do the rebuild and do it right to really end the problem once and for all. Life is too short to put up with these kinds of problems and ruins the pleasure of driving the car.
 

sprice

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When I got it from the junkyard 20yrs ago, one of the many first things I did was add a temp gauge. It would get up to 240 when it was about 85 degrees with A/C off. So I had the radiator recored, replaced the water pump, did a back flush on the system, and . . . . . . .
I purchased a 1968 Dart with a 440. Obviously not original however had mopar rad and parts. Back flushed, chemical flush, pressure flush, thought I had it clean. The black just kept coming. Removed the lower hose and could not believe what came out. I agree with the suggestions to remove the expansion plugs or seek a professional process (if possible) without risking further damage or disassembly. Suspect some caking in the block given all the front end R&R already completed.
 

Imperial Pete

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Another tip I have found (especially with engines that have sat) is to fit one of the below in line filters to the top hose. This will also save the new radiator from blocking again. Yeah it looks awful but keep checking it and cleaning it out regularly. Eventually the crud will clear and you can remove it.
They have an in line mesh filter and a magnet to catch it all. Easy to clean all you do is unscrew the cap, flush the filter with a hose.
My Imperial had sat for over 20 years, I had a new super high flow radiator made ($1200 in Australia!) so blocking a new radiator is not something I wanted. Even after flushing the block there still is a fair amount of crud in there.
Not sure if you guys in the US have these, pretty sure they also make billet ones in the US.
TEFBA-IN-LINE RADIATOR-FILTER-1-¼ 32MM RADIATOR-HOSES
 

fury fan

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I also use a Comp Cam with good low end torque to give a little added low end grunt for these 440 engines that really makes a difference in how they feel off the line while not giving up the smooth idle.

Since you brought it up, and you've given good driving testimony on a 360 vs a 383-2, and also on the 383-4 vs a 440 -- please post that cam part#?
You put it in E85s or E86s?
If only the E85, how does it make it feel vs an E86?
Or if both, how does it compare with a stock E86?
 
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