Time for a Radiator Upgrade...?

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7900_Blazer

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Thoughts on specifically what radiator you all would suggest for my 1975 Blazer... 350 engine?

Back story:

In my 'Stranded' thread from late July early August, my Blazer was vapor-locking in the Colorado mountains, partially due (I think) to it running too hot.

So now back in Texas - it was 99 yesterday afternoon - driving home from work it got up to about 220 degrees...

Went to put in a 180 degree thermostat this morning and it already had a 160 degree thermostat in it...

Left it out completely - driving in this morning, temps were around 80 degrees or so and with no thermostat, truck got up to and ran right at 195 to 198 degrees...

I think I need to upgrade my 46 year old radiator...

Note: Eventually I'm going to upgrade the SM465 to a 4L80E or a 6L80E

So, thoughts on specifically what radiator you all would suggest?
 

Bextreme04

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If you already have a brass 4-core radiator, you might just need to take it to a local shop and have it cleaned out.

Things that will absolutely make it run hot:

  • Plugged radiator
  • Water pump going out
  • Running with wrong/no thermostat
  • Running an engine driven cooling fan without a shroud(or just the wrong shroud)
  • Fan clutch not engaging at the right temp(bad clutch)
  • Engine Timing(timing being too far out will make it run HOT)
  • Air/fuel mixture not adjusted right

I would recommend before you go too far down this rabbit hole to just inspect the inside of the radiator. You can just pull the cap and look in at the inside fins and see if it is all corroded and plugged. Then I would recommend you get the correct 195 thermostat and then do a full tuneup on the engine. Inspect the full ignition system and then set the timing properly and then adjust the carb for proper air/fuel mixture at idle and while driving.
 

AuroraGirl

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Thoughts on specifically what radiator you all would suggest for my 1975 Blazer... 350 engine?

Back story:

In my 'Stranded' thread from late July early August, my Blazer was vapor-locking in the Colorado mountains, partially due (I think) to it running too hot.

So now back in Texas - it was 99 yesterday afternoon - driving home from work it got up to about 220 degrees...

Went to put in a 180 degree thermostat this morning and it already had a 160 degree thermostat in it...

Left it out completely - driving in this morning, temps were around 80 degrees or so and with no thermostat, truck got up to and ran right at 195 to 198 degrees...

I think I need to upgrade my 46 year old radiator...

Note: Eventually I'm going to upgrade the SM465 to a 4L80E or a 6L80E

So, thoughts on specifically what radiator you all would suggest?
what kind of exhaust you have? restricted exhaust can cause heat problems as well as play funny with various driveability, although, this would require your 75 which is a first year for cat mandates in cars...? not sure on trucks... might be exempt by weight.. etc.. anyway, just think about what kind of exhaust, emissions butterfly, pipe diameter, manifolds you have. they all good? That damn EFE butterfly is a known die on you quietly type

also have you added a return yet? if your mixture is maybe leaning out from the fuel temps then consider that an easy way to make it work better and kill multiple birds with a rock, you know the saying.

then what bex said.

WHAT IS YOUR COOLANT MIXTURE %, IS IT ANYTHING BUT DISTILLED AND GREEN, ARE THERE VISIBLE DEPOSITS ON AND UNDER THE CAP(check while cool, possibly deposits in reservoir that pull back in...), IS THERE ANY AIR IN SYSTEM, IS 195 T STAT IN THERE, AND DOES WP/FAN DO A GOOD AMOUNT OF HUSTLING?

How old is that coolant

Also, a colder t stat is not how you cool a hot running engine. A cooler t stat is for knock control or engines where its calibrated as such for the combustion to be the right temp, it just happens to run hotter near the that than something like an SBC.

Since you have what is not a blown out hot rod engine, I assume, spark control is not necessary because the factory design is sufficient and works, and the SBC is 195 t stat. I think big blocks are 160? Dont run a 160., that keeps your plugs too colld and they foul. fouling makes rich. rich isnt good. someone may have compensated for rich with timing advance. timing advance is also not good. you understand.
 

7900_Blazer

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If you already have a brass 4-core radiator, you might just need to take it to a local shop and have it cleaned out.


Things that will absolutely make it run hot:

  • Plugged radiator
  • Water pump going out
  • Running with wrong/no thermostat
  • Running an engine driven cooling fan without a shroud(or just the wrong shroud)
  • Fan clutch not engaging at the right temp(bad clutch)
  • Engine Timing(timing being too far out will make it run HOT)
  • Air/fuel mixture not adjusted right

I would recommend before you go too far down this rabbit hole to just inspect the inside of the radiator. You can just pull the cap and look in at the inside fins and see if it is all corroded and plugged. Then I would recommend you get the correct 195 thermostat and then do a full tuneup on the engine. Inspect the full ignition system and then set the timing properly and then adjust the carb for proper air/fuel mixture at idle and while driving.

@betreme04, thank you for the feedback.

I think it is a 46 year old radiator that needs either to be rotted out or replaced.

In the Dallas area, there are radiator repair shops... but it's $150 to $195 to repair/rott out a radiator...

So looking for specific thoughts on a replacement - if anyone has replaced theirs.


New water pump
Not sure how running with no thermostat would make it run hotter than with a thermostat that restricts flow and holds the water in the engine until it reaches 195 degrees...

Has a engine driven cooling fan.
Has the correct shroud
No Fan clutch
 
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7900_Blazer

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350
what kind of exhaust you have? restricted exhaust can cause heat problems as well as play funny with various driveability, although, this would require your 75 which is a first year for cat mandates in cars...? not sure on trucks... might be exempt by weight.. etc.. anyway, just think about what kind of exhaust, emissions butterfly, pipe diameter, manifolds you have. they all good? That damn EFE butterfly is a known die on you quietly type

also have you added a return yet? if your mixture is maybe leaning out from the fuel temps then consider that an easy way to make it work better and kill multiple birds with a rock, you know the saying.

then what bex said.

WHAT IS YOUR COOLANT MIXTURE %, IS IT ANYTHING BUT DISTILLED AND GREEN, ARE THERE VISIBLE DEPOSITS ON AND UNDER THE CAP(check while cool, possibly deposits in reservoir that pull back in...), IS THERE ANY AIR IN SYSTEM, IS 195 T STAT IN THERE, AND DOES WP/FAN DO A GOOD AMOUNT OF HUSTLING?

How old is that coolant

Also, a colder t stat is not how you cool a hot running engine. A cooler t stat is for knock control or engines where its calibrated as such for the combustion to be the right temp, it just happens to run hotter near the that than something like an SBC.

Since you have what is not a blown out hot rod engine, I assume, spark control is not necessary because the factory design is sufficient and works, and the SBC is 195 t stat. I think big blocks are 160? Dont run a 160., that keeps your plugs too colld and they foul. fouling makes rich. rich isnt good. someone may have compensated for rich with timing advance. timing advance is also not good. you understand.


@AuroraGirl thanks for the feedback - any thoughts on where you'd suggest picking up a replacement?

No, haven't added a return line yet... wanted to initially try to solve the root problem, which is heat I think (combination of things actually) however, it is very high on my list to add a return line mechanical pump and return-line sending unit.

Exhaust is stock manifolds.

Coolant is approx 50/50 and new from changing the water pump and then changing the harmonic balancer...
 

WFO

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Not sure how running with no thermostat would make it run hotter than with a thermostat that restricts flow and holds the water in the engine until it reaches 195 degrees...

Has a engine driven cooling fan.
Has the correct shroud
No Fan clutch
Without a thermostat to close when needed, the engine heat doesn't get a chance to transfer into the water, to be cooled in the radiator.
 

Bextreme04

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@betreme04, thank you for the feedback.

I think it is a 46 year old radiator that needs either to be rotted out or replaced.

In the Dallas area, there are radiator repair shops... but it's $150 to $195 to repair/rott out a radiator...

So looking for specific thoughts on a replacement - if anyone has replaced theirs.


New water pump
Not sure how running with no thermostat would make it run hotter than with a thermostat that restricts flow and holds the water in the engine until it reaches 195 degrees...

Has a engine driven cooling fan.
Has the correct shroud
No Fan clutch

You might be surprised on all of those counts. My brass radiator was the original equipment 1980 brass 4-core. It has developed a leak, but internally it looks brand new. If it has had correct coolant and distilled water in it for it's whole life, there is no reason that the inside should have any deposits or buildup affecting cooling efficiency. A standard replacement radiator nowadays will be $150-200 for a plastic tank version and $300+ for a brass replacement. Full aluminum will also likely be in the $300+ range and gives you zero benefit over either option and actually will cause a few extra issues that will need to be addressed if you go that route.

Just like your previous threads... people have been down this road, repeatedly, and you seem to ignore a lot of solid advise and then head down a rabbit hole. It costs you nothing to test and verify. It is super expensive to just throw parts at it with no understanding of what's actually going on there. You can actually be introducing new issues that way too.

Removing the thermostat can cause less heat to be removed from the engine because without the restriction, the pump will flow water through the engine and radiator so fast that it doesn't have any time to actually transfer the heat. The restriction is there to allow the coolant to spend enough time in those areas to get maximum heat transfer.

Your motor should have a 5-bladed fan and a thermostatically controlled fan clutch. Can you post some pics of what you are working with? A pic of the inside of the radiator core would be nice too... you can just remove the cap and look in at an angle, you should be able to see the number of cores and the shape they are in.

The core problem is not excess heat from the engine. The core problem is that you don't have a return line. These vehicles were know for doing this right off the lot when not equipped with a return line, that's why GM started putting the return line on all of their vehicles.
 

AuroraGirl

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@AuroraGirl thanks for the feedback - any thoughts on where you'd suggest picking up a replacement?

No, haven't added a return line yet... wanted to initially try to solve the root problem, which is heat I think (combination of things actually) however, it is very high on my list to add a return line mechanical pump and return-line sending unit.

Exhaust is stock manifolds.

Coolant is approx 50/50 and new from changing the water pump and then changing the harmonic balancer...
The core of the problem is you have gasoline that inherently is more volatile snd less thermally stable at the same temps as the gas the truck was originally using which was itself problematic from day one.
3969837 Is a gm part number for a Quadrajet
9266 for edelbrock
If you want to test our recommendations against your deeply held ideas, put a spacer in that breaks 1) the conductive energy transfer with a material that doesn’t transfer thermal energy well between the carb and engine, then use a heat shield to baffle radiant energy from going toward it so easily, then wrap your fuel line and pump best you can with insulation for heat (home improvement store would have something) amd then try driving around in this same weather.

you will show some improvement if you out your stat back in.

on the t stat, the coolant water pump is damn good at circulation especially with a smaller pulley size (can we see your crank pulley and water pump pulley relationship too) name if it’s new, it’s probably high flow just from less wear. The coolant itself is kinda ****** at the heat transfer thing because of the alcohol. The reason we use it obviously is the cold protection and the additive packages for our cooling system.

but because it can’t transfer as well, it needs to be held in the side with hot stuff, an engine, to take that heat, then it gets cycled over to the radiator, where it hangs out giving its energy to the large surface area and air flow, and over to the heater core too even with no fan it’s sharing energy. If it flowed right past it wouldn’t release much or pick up. ESPECIALLY In cast iron,steel. And brass radiators. Brass is less thermally efficient as aluminum radiators I believe due to the need to solder which is usually tin or lead which isn’t as good, reducing efficiency, and the size of fins, walls, etc are usually thicker which makes for repair easy parts but not cutting edge efficiency.


My park avenue, for example, had no stat for a 2 day period while I was flushing system with thermocure. It ran cold as **** despite being September and rather warm because the engine when not in boost has such a low compression ratio and a large radiator, aluminum, 2 cooling fans, and at this point the inside was much cleaner too, which has a aluminum manifold and etc. it actually runs cold in winter by this nature and I have to block the radiator some amd if it was a really hot summer, I would have a 180 stat which is for reducing knock retard and reducing the overall temps because swampy weather and my affinity for induction noise WILL result in the computer taking your timing back real hard to prevent “chipped pistons” and “spun rod bearings” or “installing new drain locations” in the block. Which it over compensated fr, but not without some reason. That’s an example of 180. 180 becomes 195 when it’s temperate or cold. For efficiency, economy, plug life, and to keep the engine from taking in water but never evaporating it.

that same cold running park avenue with more efficient cooling system?
Sit in traffic with that missing t stat and even cold out, watch it climb. The car has been able to take it, but only after having to runs the fans on constant high power (that’s a lot of amps btw and requires the pcm to see 225 without a rate of cooling it finds comfortable ) especially in gear because the transmission says hello to the coolant with its very efficient water to water transfer instead of water to air of the radiator and the water pump pulley is small so it spins a good amount at low speeds.
 

7900_Blazer

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You might be surprised on all of those counts. My brass radiator was the original equipment 1980 brass 4-core. It has developed a leak, but internally it looks brand new. If it has had correct coolant and distilled water in it for it's whole life, there is no reason that the inside should have any deposits or buildup affecting cooling efficiency. A standard replacement radiator nowadays will be $150-200 for a plastic tank version and $300+ for a brass replacement. Full aluminum will also likely be in the $300+ range and gives you zero benefit over either option and actually will cause a few extra issues that will need to be addressed if you go that route.

Just like your previous threads... people have been down this road, repeatedly, and you seem to ignore a lot of solid advise and then head down a rabbit hole. It costs you nothing to test and verify. It is super expensive to just throw parts at it with no understanding of what's actually going on there. You can actually be introducing new issues that way too.

Removing the thermostat can cause less heat to be removed from the engine because without the restriction, the pump will flow water through the engine and radiator so fast that it doesn't have any time to actually transfer the heat. The restriction is there to allow the coolant to spend enough time in those areas to get maximum heat transfer.

Your motor should have a 5-bladed fan and a thermostatically controlled fan clutch. Can you post some pics of what you are working with? A pic of the inside of the radiator core would be nice too... you can just remove the cap and look in at an angle, you should be able to see the number of cores and the shape they are in.

The core problem is not excess heat from the engine. The core problem is that you don't have a return line. These vehicles were know for doing this right off the lot when not equipped with a return line, that's why GM started putting the return line on all of their vehicles.

@Bextreme04

Not ignoring your advise...

Maybe I am.. because I do not think adding a return line is going to lower my engine operating temperature from 220 down to say 180 or 190 - maybe it will though and I'm completely wrong... won't be the first time.

I did ask a specific question that has been ignored - but that's fine...

Still I do appreciate the thorough feedback. I have a 180 degree thermostat that I can put in v.s. the 160 degree one that I took out when it hit 220.

Do you think changing from the 160 to the 180 is the problem?
 
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7900_Blazer

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The core of the problem is you have gasoline that inherently is more volatile snd less thermally stable at the same temps as the gas the truck was originally using which was itself problematic from day one.
3969837 Is a gm part number for a Quadrajet
9266 for edelbrock
If you want to test our recommendations against your deeply held ideas, put a spacer in that breaks 1) the conductive energy transfer with a material that doesn’t transfer thermal energy well between the carb and engine, then use a heat shield to baffle radiant energy from going toward it so easily, then wrap your fuel line and pump best you can with insulation for heat (home improvement store would have something) amd then try driving around in this same weather.

@AuroraGirl Help me understand 'what deeply held ideas I'm holding onto?'

I think 220 degrees is too hot - for my 1975 350... is that what you mean - just want to understand.

If my truck has a new water pump, factory shroud, 50/50 mix of coolant and water, fan clutch isn't slipping (no clutch) and it had a 160 degree thermostat.. and it is running at 220 on a hot Texas day... then are you suggesting a 180 degree thermostat is likely the issue vs needing work on the radiator? Seems like its down to those two right?
 
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Bextreme04

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@Bextreme04


Not ignoring your advise...

I did ask a specific question that has been ignored - but that's fine...

Still I appreciate the thorough feedback.

No one can give you advice on what specific radiator is a good upgrade for you when we don't know what you have now. Pics are always helpful. If you have a large 4-core brass radiator, then there is no real drop-in "upgrade". You will already have the best option available at that point. If you have a smaller radiator, then upgrading the radiator will also likely require a different upper radiator mount, different fan shroud, and different fan... so keep that in mind.

I have the big 4-core in my 1980 K25, but I upgraded to the factory 97 454 radiator and dual electric fans in preparation for my 454/4L80e swap. It is literally the largest radiator you can possibly fit in there while still being able to use the factory air inlet and AC lines. I had to weld in the lower radiator support section from the donor rig into my original core support and also clearance the steering gear box a little bit, but it actually fits in there really nicely.

I am doing the final paint on the core support tonight, so I can maybe post some pics. It's probably more involved than what you are looking to do right now anyways though.
 

7900_Blazer

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No one can give you advice on what specific radiator is a good upgrade for you when we don't know what you have now. Pics are always helpful. If you have a large 4-core brass radiator, then there is no real drop-in "upgrade". You will already have the best option available at that point. If you have a smaller radiator, then upgrading the radiator will also likely require a different upper radiator mount, different fan shroud, and different fan... so keep that in mind.

I have the big 4-core in my 1980 K25, but I upgraded to the factory 97 454 radiator and dual electric fans in preparation for my 454/4L80e swap. It is literally the largest radiator you can possibly fit in there while still being able to use the factory air inlet and AC lines. I had to weld in the lower radiator support section from the donor rig into my original core support and also clearance the steering gear box a little bit, but it actually fits in there really nicely.

I am doing the final paint on the core support tonight, so I can maybe post some pics. It's probably more involved than what you are looking to do right now anyways though.

I'm going out to grab some pics before going home.. will post up in just a moment...

thanks again!
 

7900_Blazer

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Some pics

Video at idle: https://youtube.com/shorts/h4IMsrPxSlI?feature=share


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