Radiator question
 

I'm chasing an over heating issue with my 53 pickup. I thought I knew the answer to this question before a friend asked me if I was sure......all of a sudden I wasn't.

What is the normal flow route of hot water. I thought it was hot water into the radiator from the top when the thermostat opens and cooled water out from the bottom of the radiator sucked up by the water pump to the block.

For some reason, when he asked if I was sure, I blanked out.

Re: Radiator question
 

What engine do you have? If it's a sbc, that is the correct flow. Remember, heat rises

Re: Radiator question
 

I have a 261 straight six

Re: Radiator question
 

When is it overheating?
At around town drive or on the highway?

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And what temp does it get to?
And do you have a closed or open cooling system?

Re: Radiator question
 

I have had it out two times for drives of modest distance. The first was about 20 miles of city driving, with some stop and go at traffic lights. It heated up to 180 after five or six miles, then to 200 about five miles after that. When it hit 210, I pulled over and let it cool down for 15-20 minutes. When I got to my destination, it was back up to 210 +/-

The second drive was about 10 miles, with only one or two traffic lights. The truck ran in the 160 to 180 +/- range for almost 8 miles, then up to 200 for the final few miles. Unfortunately, I was then in stop and go traffic getting to my spot at the car show, and it went to about 210 before I could shut it down.

At this point, I have done the following things:
- adjusted the carb mixture to be richer
- check my timing to ensure it hasn't been overly retarded
- adjusted my electric fan to come on at 160 instead of 180
- changed the thermostat from a 180 degree to a 160 degree
- removed the AC condenser from in front of the radiator
- moved the pusher fan (3,000 CFM) to directly in front of the radiator

There is no room for a puller fan behind the radiator given the clearance between the rad and the supercharger, alternator, compressor, and harmonic balancer.

I am in the process of fabricating a shroud to fit on the front of the radiator to hold three 11" pusher fans for a total of 6,000 +/- CFM. Theoretically, I could fit another 11" fan on the back side of the radiator off to one side, but I'm going to hold on that pending the results of the 3 - 11" fans.

Here is a photo of my mock-up shroud.

Attachment 2423618

The current electric fan is a

Re: Radiator question
 

You might be blocking more air with that shroud.
When the hood is closed do you have a tight seal between it and the rad?
Sometimes electric pusher fans will tend to circulate hot air back to its inlet from over the top of the rad.

Re: Radiator question
 

I'm a big NO on that thing. I have never seen anything like that used with a pusher fan on any rig. That will make it overheat at road speed let alone at and idle or low speed.

Re: Radiator question
 

The hood has louvers cut in on both sides in terms of airflow


Should I just use the zip tie things that came with the fans to mount them directly to the rad?

Re: Radiator question
 

The fans cover 80% of the shroud. I could cut openings in the remaining areas to allow air to flow, but even if I use fans alone, they will cover 75-80% of the surface area of the radiator.

Re: Radiator question
 

Something I’ve had success with is an air dam mounted directly below the rad. About 4-5 inches in height.
Creates a low pressure area behind the dam allowing a place for the hot air to flow to.

Re: Radiator question
 

Well All I can say is do what you are planning and let it be a learning experience.

On the zip tie thing I AM NOT A FAN IN THE LEAST BIT I've replaced a couple of radiators on people's cars that had things tied to them with those plastic pegs. One was a big honking transmission cooler that a guy put on his truck and the ties wore through the tube on the radiator. He just had me repair the radiator because the radiator shop was so far behind that his truck would be down a lot lot longer than he could do without it during harvest.

After I had that piece of aluminum with a ton of holes cut with a hole saw that still blocked way too much air I put two pieces of 1 inch flat bar across from side to side and fastened the fan to them.

The thing is that fans of any kind usually go out of play when you hit 40 or so or are cruising down the highway at 70 or so unless you are pulling a grade or pulling a load. I lived in McGregor for the first 8 years my wife and I were married (still are #56coming in August) and know Texas heat and you flat need air flow at road speed. You may pull more air at a crawl with that setup but at 70+ it will block a lot of air.

Re: Radiator question
 

261s seem to build heat fast, we were testing my son's PS setup at idle without a rad fan and it boiled within a minute.
You are running the full hood latch panel and lower grill support panel, so the air isn't just by passing rad?
Waterpump pulley and crank pulley are stock sizes?
Does it cool down quickly if you pick up speed and stay cool at speed?

You could try your three fans with just the zip ties as a proof of concept before adding the shroud. If you do the shroud, you could add rubber flaps in the blank areas....SPAL 30130012 or similar.
I would not run the zip ties as more than a test, in my experience they do not hold. I replaced zip ties with 3mm SS threaded rod and nylocks on a off topic swap. Keep the rubber gaskets under nuts/fans so nothing vibrates around....cutting into the core is a fear. I like the idea of a shroud less mount that hold fans close to rad.

I like geezer#99's air dam idea, worth a test. I might try that later this summer. Maybe a drive with the hood off would confirm if the problem is fixed with better air exit.

I have 2 * 12" puller fans cooling the 250 in my 52 with a shroud something like yours. stop and go traffic gets hot. I added slots in shroud to improve low speed cooling. It helped. I also have a switch on dash that turns the fans on regardless of thermal switch - I just leave them on in stop and go so it does not cycle up and down.

Re: Radiator question
 

I'm going to experiment with flat bar to see if I can arrnge the three fans using that method.

Alternatively, I have found 16 guage aluminum that is perforated with 1/8 holes over its entire surface.

Re: Radiator question
 

on my 48 I have been thinking about running a larger electric fan as a pusher on the top half of the radiator and running as large of a one as I can put in there probably off a Dodge mini van to supplement the too small fan that you can fit on a later six in the AD trucks. The GMC radiator just gives me more space between the radiator and the fan but doesn't allow for a larger fan.

Still I believe that what you are planning will cause more issues than it fixes. You have to have that free unblocked air flow over 35/40 mph.

Re: Radiator question
 

So far with a 16 in pusher and loads of open radiator space, the truck still over heats both at a standstill and moving. Admittedly, the high temps are worse at a standstill than moving. But I have got to do something to get more cooling capacity to the radiator.

Theoretically, I can fit one additional 11" electric puller fan on the top (drivers side) of the radiator. I'm just not sure that a pusher and puller on each side of the radiator will make that big of a difference. I guess I could wire the puller to a switch in the cab and let the three pushers up front continue to be thermostatically controlled......

Re: Radiator question
 

Is the radiator large enough; does it cool at speed under load?

With the supercharger, power steering? and AC you have, plus the flat plate mounting bracket, is there enough airflow past the motor? geezer#99s suggestion of a dam under rad again.

Re: Radiator question
 

While it is a stock size radiator, it is all aluminum. I had to have it custom made due to the traditional lower return pipe being in the way of the supercharger belt and idler pully. Ron Francis Racing had the dimensions for the traditional radiator and moved the return port over to the driver side.

Power steering is an electric unit, much like a Prius or Telsa, so it has no effect on the engine. At this point the AC compressor is just free spinning since, I removed the condenser, so the crank spins the supercharger belt and the water pump and compressor belt. The compressor has double V grooves and there is a separate belt to drive the alternator.

As far as a dam is concerned, I know what they are, but I'm not sure I understand where its being suggested that I mount it.

Re: Radiator question
 

Mount the dam directly under the rad.

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What material have you used to fabricate the air dam?

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He still has the original frame and original apron in front of the radiator and not a cobbled up S-10 swap with a butchered apron.

He is just trying to do something that I firmly believe will hurt more than help but he will figure that out with one drive down the highway and if the engine didn't overheat too bad will go back to square one and call it a learning experience.

This is the pusher fan that fits a 91 Dodge Grand Caravan with a 3.3 V6 like the all wheel drive one that I would probably still have if my wife hadn't wrecked it as it was the best all around vehicle I ever owned in all my years of owning cars and trucks. That fan will move air and doesn't block air flow. Plus they aren't expensive and it will cover the top part of my radiator from the front side while my fan on the water pump will cover the lower part.

Re: Radiator question
 

The first one I did was on a 70 chevelle. Adapted a dam from a 76 nova.
Later ones I used plexiglass mounted with strap iron.
FWIW the dam was suggested by a retired nascar guy. He used one to help cooling his Boss 429 he squeezed into his 68 short box merc.

Re: Radiator question
 

If I can find a piece of plexiglass I will do that, otherwise I've found a cheap air dam for a Camaro online that I can cut and fashion to work.

Re: Radiator question
 

try asking the plastic supplier before you use plexiglass. it is relatively brittle so if it takes a rock it may shatter. maybe something more durable could be used, from the plastic store. UHMW (ultra high molecular weight) maybe? puck board is usually cheap (the stuff they use around hockey rinks) if you want something just to see if it works.

Re: Radiator question
 

I found an inexpensive air dam from a Camaro that I'm going to shorten to fit my needs.

Re: Radiator question
 

Unless that radiator is plugged, it should be more than capable of cooling the engine. Between aluminum construction and sheer size you should be more than covered at low load. Pusher fans are fine but I would try to build simple box or tube shaped ducts between radiator and fan to prevent air dispersing rather than install a shroud that restricts airflow when moving. And yes, the shroud in the pictures is very restrictive.

An air duct under the radiator can be very effective. The goal is to create a low pressure pocket behind the dam which draws air down through the engine comparment. It can be so effective that you can see the hood get sucked down on the highway. If the truck is overheating at idle the air dam is not the answer.

I'm not sure why folks say retarding timing will cause overheating. This is generally not true. When spark occurs it initiates a reaction which takes time to complete. We use spark advance to try and match peak combustion pressure to crank angle at 6-20 degrees after TDC. We start combustion before the crank is at TDC and the reaction continues even after the piston reaches BDC.

Retarding timing will effectively make peak pressure occur at a greater amount of crank degrees ATDC. To a point, the crank angle is greater, mechanical advantage created by the lever arm of the crank is greater, and cylinder pressure is lower but more effective. This means less wasted energy is used to heat the pistons, head, and block. But it also means the combustion reaction continues into the exhaust and can heat headers / manifold.

If spark is advanced we see a different result. Pressure begins to increase as the piston is forced to TDC by the crank. Pressure created by combustion attempts to force the piston down the bore while momentum and force created on other pistons is working to move the piston up. If there's too much spark advance we start to see big pressure spikes and heat as the "up piston" and "down piston" forces in the engine collide. First, engine oil endures extreme pressure as the rod bearing is forced toward the crank. This very quickly heats the engine oil which can result in oil thinning and even contact between bearing and crank. If the engine continues to operate with excess advance, energy that cannot be used to move the piston down is shed in the form of heat. The piston tops, cylinder head, and block are be quickly heated. Heat will transfer out of these parts but it happens more slowly than it is being added. The only way for pistons to cool are through contact with oil, by splash or from oil cooling jets, and by contact with the cylinder walls and minimally through windage. The primary cooling method for the heads and block is through heat transfer, first to coolant then to radiator then to air. It's very slow and can easily be overwhelmed. If you have old, heavy cast heads and / or a block with poor circulation paths it only delays heat transfer. And if any steam pockets form, well, you've just reduced heat transfer to near zero in those areas.

The absolute best approach is to reduce the amount of heat that's transferred to the heads, block, and piston. Especially on an engine that doesn't need to achieve maximum power or efficiency. I can tell you from experience that 2-3 degrees too much advance at cruise is enough to quickly take out bearings on a forced induction engine without any audible or performance signs there's a problem.

I would not be afraid to reduceg peak advance by 2 - 3 degrees and then monitor coolant temp. I would seriously consider installing an oil temperature gauge to monitor the effects of timing changes and changes in weather or fuel. And I would think about using a "wide band oxygen sensor" to check the air:fuel ratio of the engine as it operates through idle, acceleration, and cruise. Either I would buy one to use while driving or I would rent time on a chassis dyno. These tools and methods are frequently used in todays world of EFI tuning. When these tools are used correctly engines achieve higher levels of power without sacrificing reliability.

I would also consider adding an engine oil cooler to help ensure engine oil is not overheated. The engine oil cooler could be placed in a different location so as not to affect air intended for radiator cooling. An oil cooler placed under the radiator, like an air dam, might be very effective.

Your mileage may vary.

Re: Radiator question
 

The saga continues, but hopefully I have the problem on the run. Here is what I have done so far to get a cooler running truck.

1) Adjusted timing
2) Installed a 160 degree thermostat
3) Replaced the multi-section lower radiator hose with one with spiral coil inside
4) Temporarily removed the AC condenser to get a free flow of air to the radiator
5) Re-gapped my spark plugs, not sure this does anything, but it is a change
6) Installed an air damn directly under the radiator support
7) Went from one pusher fan of 3,000 cfm, to three 2,000 cfm fans for a total of 6,000 cfm

Attachment 2424928

Attachment 2424929

I'd be driving it right now, except I seemed to have misplaced a plastic insulator that goes between the magneto cap and the internals. Until the replacement shows, up I can't run the car. It shoud be here by this weekend, so more to come......

Re: Radiator question
 

you mentioned you replaced the lower hose with one that has a coil inside. Does the top one also have a coil? If there is no coil in either hose, they could be compressing and causing a flow restriction, there by causing an over heat problem. I had a 392 hemi that had what sounds like the same problem. The correct hoses solved the problem.

Re: Radiator question
 

Running a 160 degree thermostat is going to hurt you, not help you. It may take the engine a while longer to overheat, but you're reducing your cooling capacity with this thermostat. A low thermostat isn't doing your engine any good either.

The rate of heat transfer out of a radiator is always a funtion of the temperature difference between the radiator and the outside air. To maximize heat transfer you want the radiator as hot as possible relative to the air going over it.

6000 cfm of fans is likely overkill and your truck is going to sound like a vacuum cleaner going down the street, especially if they're in front of the radiator. Doubling or tripling the flow through the radiator isn't likely to make it cool much better and will just make it noisier - cooling capacity isn't linear with flow velocity

I'd suggest that you install a PWM fan controller with a temp sensor to slow the fans down and match demand.

Also, water has better heat transfer than antifreeze. I'd only use as much antifreeze as was necessary to protect from freezing in your area and no more. The ideal situation would be water and some Lubeguard for corrosion protection, pump lube and some wetting agents.

Just my 2 cents...............