Overheating Help?


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Yard Art
Yard Art

Posts: 59

Joined: Wed Aug 02, 2017 11:17 am

Post Mon Jun 11, 2018 9:20 am

Overheating Help?

I'm hoping someone has some ideas on my overheating issue. I put my KB-7 cab, grill and hood on a 69 Chevy C-40 with the 292 six and a 4 speed. The Chevy ran good before the conversion with no overheating. I had to use the KB radiator as that is what fit in the grill assembly. I had the radiator cleaned and tested and some misc. issues repaired and was told it is a low pressure radiator and to use the 4 lb cap. Because the radiator is very close the the water pump, I could not use the Chevy fan and I installed an electric fan in front of the radiator, pushing air through. The fan runs whenever the key is on. the air flow seems good as you can feel a lot of air moving through the radiator when it is on. I tested and used the 190 degree thermostat.

The old girl runs good until I come up a big hill, and we have a lot of them in PA. I am down to 2nd gear at 25 mph, working hard for sometimes 2 miles on these hills.Then it over heats and pushes coolant out the overflow tube. I have picked up a new 4lb cap to try, a 160 degree stat to replace the 190, and a supplemental more accurate temperature gauge to install until I get this issue resolved. I am wondering if the fan provides enough air movement when working hard, and will I have to consider installing another fan?

I know IHC fans have a lot of collective knowledge regarding all things mechanical! Any thoughts? Thanks.

Site Admin
Site Admin

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Location: Nampa, Idaho

Post Mon Jun 11, 2018 3:25 pm

Re: Overheating Help?

Did you flush out your 292 motor? Perhaps some passages are plugged? If you have done the two changes, How much area of the radiator does your current fan cover? You might need another one. One other thought, you might look to one of the aluminum radiators that would fit in your space.

Rusty Driver
Rusty Driver

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Post Mon Jun 11, 2018 3:55 pm

Re: Overheating Help?

Could the engine maybe get starved and can't push water when motor is at an angle?

Freshly Restored
Freshly Restored

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Location: Western NY

Post Mon Jun 11, 2018 4:49 pm

Re: Overheating Help?

When you're down in 2nd gear and turning a lot of RPM to make it up the hill it could be sucking the bottom radiator hose flat and cutting off the flow
'48 KB-1 Service Truck, '96 Dodge 3500 4x4 Cummins Dually Flatbed
'55 Willys CJ5 Jeep, '49 Chevy 3600 Deluxe
If you can't fix it with a hammer, it's an electrical problem

Golden Jubilee
Golden Jubilee

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Post Mon Jun 11, 2018 4:51 pm

Re: Overheating Help?

These electric fans are up to 20% more efficient if they are mounted behind the radiator. Changing the thermostat to 160 F from 190 F is a waste of money, for you. The thermostat sets the low temperature, ONLY.
It sounds like you cheeped out on the radiator. If your rad is an original it has 70 years of use and no amount of boiling will make it new again. There will be some thin surface corrosion inside the radiator and this is a really good insulator. Your radiator cannot transfer heat to the passing air.
Someone suggested one of the eBay aluminium radiators. I hear good things about them. My friend has one of those eBay rads in his IHC K pickup. His engine is a BBC 454/400 automatic.

1) crappy radiator. OEM radiator not efficient enough for more powerful motor. Power makes heat.
2) less then best positioning of the electric fan
3)
I would rather have tools I do not need than to need tools I do not have

Yard Art
Yard Art

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Joined: Wed Aug 02, 2017 11:17 am

Post Tue Jun 12, 2018 7:27 am

Re: Overheating Help?

Thanks for the help everyone. Did not flush the block, but had no issues before. Jim, maybe the fan is too small.

Nikinut, I like your reasoning. I knew this would be a bit of trial and error, then corrections. I included a pic of the fan from a donar vehicle mounted in my grill. Maybe it is not big enough, I see they make double fan models from jegs. I only have about 3 inches between the water pump and the OEM radiator I am currently using. Will the Ebay aluminum radiator fit in my grill assembly? Wonder if I should try a bigger fan first, or cut my losses and just purchase a whole new fan/rad assembly. I only have $60 into this radiator/fan combo.
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Last edited by brianz on Tue Jun 12, 2018 7:41 am, edited 1 time in total.

Yard Art
Yard Art

Posts: 83

Joined: Wed Dec 30, 2015 9:43 am

Post Tue Jun 12, 2018 7:41 am

Re: Overheating Help?

Would you be able to get two smaller fans in between the engine and the rad? The one you have in the picture is too small. You have pieces of tin blocking off airflow on both sides of the fan. Also shrouding the fan helps. Other wise the airflow just spills out the sides.

Yard Art
Yard Art

Posts: 59

Joined: Wed Aug 02, 2017 11:17 am

Post Tue Jun 12, 2018 7:43 am

Re: Overheating Help?

Got about 3 inches of clearance water pump to OEM radiator.

Does anyone have a link to a radiator/fan until that will fit in the grill without a lot of fabrication?
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Golden Jubilee
Golden Jubilee

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Location: Central Florida

Post Tue Jun 12, 2018 8:39 am

Re: Overheating Help?

I think you have two avenues of approach here. Trying to get enough fan surfaces/speeds to cool the radiator or get a radiator sized to handle the new requirements. There are ways to get bigger rads in place to do the job. A new rad will obviously set you back more cash, but if you buy from a reputable supplier, they will build it to the space you need to install it in and it will get the job you need done. You can spend money on fans you think will work (and you may be successful) but what if that doesn’t work? My advice is to consult with companies that will engineer and build a rad to do the work and if they think you need to supplement the cooling with an electric fan (and you will, especially if the mechanical fan has been removed). A key element in designing heat exchangers is the residence time to allow for cooling. Your low pressure smaller rad may not have the size (capacity/residence time) to allow enough cooling. Pressure plays a big part in the heat exchange process, too. The 292 probably had a 12 or 13 lb pressure need and now you’re asking it to survive on 4 lb and maybe less residence time. That engine needs the amount of radiator it had in its original configuration. What you need is to figure out how to get that amount of cooling under the new engine bay constraints. And Nikkinutshop is correct. The air pulled through the rad is more efficient than air pushed through. One thing to watch out for is the speed of the fan can affect the air passage. A slow moving fan can act as a blockage to air movement under certain conditions where the air coming in is faster than the fan can “boost” it along.
One of the things I’ve learned by putting a bigger, hotter engine in an older engine bay, is that the amount of air coming in through all the places it can get in - grill, under grill, wherever - needs to be able to pass all the newer volume of heat out of the engine bay. Otherwise, the heat buildup under the hood is higher than originally designed and therefore the radiator is going to see that extra load, too. If I had known then what I know now, I’d have added louvers in the inner fenders to allow for more air passage.
L110 owner since 1974, finally rebuilt 2014.
I was addicted to hokey pokey, but I turned myself around!

Golden Jubilee
Golden Jubilee

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Location: Canada's left Coast

Post Tue Jun 12, 2018 10:16 am

Re: Overheating Help?

That fan is a shrouded design. This fan appears to have the shroud as part of the fan blades. This is not uncommon.
I did not get the impression that the fan was close to the radiator, but left hanging somewhere in the grill. I am out and about presently and I don't have access to my pictures of my fan mount and installation. The lower radiator hose collapse can happen and can be easily remedied by rolling some 16 gauge wire into a coil of a size that fits snugly the inside of the hose.
Try to have the original radiator rebuilt. Ask if it is possible to add an extra row of tubes. While extra rows of coolant tubes is a good idea, this can cause an increased restriction to air flow. An extra row of coolant tubes will allow the coolant to stay in the radiator longer (resident) and transfer more heat.
Maybe you are starting to understand that every change does not stand alone. Engineering something is that way. The finished working machine is a collection of parts that cooperate and work together.
I could tell some stories from work. But I will not.
Last edited by nikkinutshop on Tue Jun 12, 2018 11:50 am, edited 1 time in total.
I would rather have tools I do not need than to need tools I do not have
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