overheating issues

[Plumcz71]

I have a 71 Roadrunner with a newly rebuilt 440. I have a 26 inch aluminum radiator with a 16 inch fan. I can run her on the freeway all day and it doesn't heat up over halfway. But driving through the city in stop and go traffic takes it right below the last mark before hot. It has a 4bbl with an Edelbrock intake and headers. I've also added power steering and power disc brakes. My mechanic says the engine tolerances were built street tight, and some more miles on it will loosen it up. Also, when she's past the first mark, the starter motor won't turn it over until it cools down some. Should I talk with him about correcting the ring tolerances or is there an additive I can add to help? Its a 71 block with a fairly aggressive cam tuned out about 10 decrees to keep it from pinging on 91 octane gas. Any suggestions?

 

[SlinktRR]

overheating

Timing?
do you have a fan shroud? If not, get one. Makes a huge difference.
the starter problems are from radiant heat off the headers. Consider a heat shield for it, make sure its non-conductive type.
oil pressure?

 

[cobrat93]

I have more questions than answers on this.....
1) What starter are you using, mini high torque starter, or stock O.E. type?
2) What thermostat are you using, 160, 180, 195 degree?
3) What kind of 16" fan are you using? flex, clutch type, static or electric?
4) do you have a fan shroud?
5) how close to the radiator is your fan?
6) What type of coolant do you use? straight water, 50/50 mix antifreeze with tap water or distilled?

 

[Dennis H]

Define overheat. Use a laser temp gun to be sure.

 

[super-bee_ski]

The understanding is:
1. Overheats at highway speed=Not Flow issues (at speed, radiator is getting cooled by forced air)
2. Over heats in city & stop N go+Flow issues (stopping and going, city traffic overheat=flow issues)

Look for:
1. No fan shroud
2. Radiator needs "Rodded out"
3. Water pump issues

 

[khryslerkid]

How many times have you heard of a person taking out the aluminum rad and installing a factory type, to solve this problem?

 

[MarPar]

How many times have you heard of a person taking out the aluminum rad and installing a factory type, to solve this problem?

more than I can count...

 

[super-bee_ski]

Plenty of times....
Funny thing is:
The manufacturers of Aluminum radiators WANT us to purchase them.
Every magazine has advertisements spewing the virtues of "Aluminum Radiators"

It only benifits the compaby...
In my honest opinion.

 

[Plumcz71]

Thanks for the input guys. Her are a few answers to the questions. We started with a 22 inch rad no shroud and flex fan after the build. Switched to a 26 in rad with a shroud and flex fan. Still ran hot then we installed the 3 core 26 inch aluminum rad with a shroud and 2 12 inch electric fans. Made it worse. so we took off the shroud and put on the 16 inch electric fan on the rad no shroud. That's what is there now. The starter is a mini high torque type and insulated from the header pipe to avoid (hopefully) heat saturation. It runs 50/50 coolant and water, not sure if its distilled or not. I believe its a 160 t stat but I'll check. I am also getting a laser temp reader to get more accurate measurements. I'm going to discuss the timing with my mechanic today and see if that is part of the issue.

 

[Histoy]

I would put the shroud back on with your new 16" fan. As previously noted, a fan shroud makes a big difference. My car has a foam rubber seal between the upper tank and the radiator support which forces all the air to go thru the radiator. If your car doesn't have one, you might consider adding one.

When your engine was rebuilt, did you change the water pump housing from factory to an after market supplier? I've heard that some of these do not flow water as well as the original Mopar water pump housings.

Another option to consider is Water Wetter, providing you don't have any type of radiator / block sealer in your system.

 

[mr. b]

check your pulleys my friend had same problem with billet pulleys he put stock ones back on no more problems

 

[Dennis H]

180 Superstat minimum temp. Probably a 195 for that year.

 

[cobrat93]

I agree, I would reinstall the shroud with your current set up. I have had good luck with Redline Water Wetter, it actually works.....
I have a 71 Road Runner with a built 440 in it as well, but I run the stock 26" Radiator with a flex fan, but am switching to an electric fan this summer, I had planned on still using the stock shroud.
I also run a high torque mini starter (without any insulation) and have had the same issue with it not wanting to crank when it's hot. I replaced the positive battery cable and the starter relay and have been trouble free for the past two years (knock on wood, lol!)

 

[MarPar]

I have had good luck with Redline Water Wetter, it actually works.....

x2! brought mine down some 15*

 

[Plumcz71]

Well, my mechanic is working on it. Putting the shroud back on, changing the water pump to a 7 blade, replacing the 160 tstat with a 180, trying Water Wetter. If that fails, it's time to see if the tolerance are too tight. It's got 1400 miles on the theruild, so that should have worked it's way out by now. I'm wondering if the headers vs. stock exhaust are part of the problem, keeping too much heat in the engine bay.

 

[coloradodave]

" I'm wondering if the headers vs. stock exhaust are part of the problem, keeping too much heat in the engine bay. "

Take off the hood and drive it to see if it makes a difference. If the car cools fine at speed then the radiator is sufficient and doing its job. The suggestions above, having to do with pulley size, radiator to hood seal, water pump housing / pump, heat gun, shroud and fan are good places to look. I use a Mopar 18" 7 blade fixed fan (no room for a clutch) and an aftermarket shroud with my Mancini aluminum radiator and don't have any cooling problems. BTW, Monday it was 106* and I was driving in traffic for a good part of the day...

 

[Bruzilla]

Another problem you might be having is you're using a 26" radiator in an opening made for a 22" radiator, which means 2" on either side aren't getting any air, which means they aren't getting cooled, but are right up against a lot of hot sheetmetal so they're impacting how your coolant is being cooled. Radiators are designed to remove heat using air on a continuous basis as the fluid moves through the radiator and going from cool to warm to cool doesn't help.

Also, a shroud is must because it forces the fan to pull cool air through the radiator, which drives the cooling when the car isn't moving. When you have no shroud the fan is moving hot air from within the engine bay and not pulling enough air through the radiator, and the direct air going to the engine is getting blown all over the engine bay instead of being focused on the engine.

The big thing is you need to make sure you're optimizing airflow through the radiator and onto the engine, with that air coming from the front side of the radiator and not from inside the engine bay, and use a radiator that's sized for the radiator opening because having tubes with no air flowing over them are not efficient for cooling.

 

[coloradodave]

Ski: Manufacturers of copper / stock radiators don't want us to buy them? Again, the fact that the car cools going down the road indicates that the radiator (aluminum in this case) is doing its job.

 

[67 coronet]

remember guys,the size of the fan dont mean crap.how much cfm does it pull?my setup pulls 4800 cfm with a very stout eng and wont get over 200 deg in traffic during 110 temps here in vegas.26 inch alum rad works great.just make sure the air is getting over it at idle.

 

[Bruzilla]

The question isn't how much CFM but where is the air coming from? If the fan is pulling ambient air from the engine bay, instead of outside air through the radiator, the car won't cool when stopped.