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upgrade radiator on '74 K5

My general thought is that with properly working components, if you can't keep it at 160* with a 160* t-stat, you won't keep it at 195* either. The cooling system is inadequate.

I've had vehicles that couldn't be overheated...the temp was rock solid regardless of load or ambient temps.

In some cases there might be an equilibrium reached as the temperature difference between ambient and coolant temp gets so large that the radiator becomes efficient enough to control the heat generated, but I doubt it. Normally the problem is a vicious cycle, that once started, cannot be stopped except to lower the load. As you note the air inlet on the trucks is relatively small. GM's solution seems to have been adding capacity...even on the later trucks they didn't change the dimensions of the core support cutouts, but if there was an additional load, coolant capacity was increased. I'm sure that some of the additional core space contributed to cooling, but it can't be anywhere near as efficient to the section of the radiator core exposed to straight through airflow. Wish I could find a photo of those that really made it apparent, this is as close as I can get: http://s18.postimg.org/9l5xeid89/engine_bay_3.png The furthest hole towards the driver fender (past the last bolt, you can see the threads in it) is the outermost bolt for the "big" radiator. That is far beyond the cutout in the core support.

I think it would be interesting to use a coolant reservoir of a gallon or so to see if that would change things in vehicles that have problems with heat under certain conditions. I measured the coolant capacity of a radiator for an 80's Corvette, as I recall it was 1.5G, which IMO is not much capacity.
 
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dyeager535 said:
As you note the air inlet on the trucks is relatively small. GM's solution seems to have been adding capacity...even on the later trucks they didn't change the dimensions of the core support cutouts, but if there was an additional load, coolant capacity was increased. I'm sure that some of the additional core space contributed to cooling, but it can't be anywhere near as efficient to the section of the radiator core exposed to straight through airflow. Wish I could find a photo of those that really made it apparent, this is as close as I can get: http://s18.postimg.org/9l5xeid89/engine_bay_3.png The furthest hole towards the driver fender (past the last bolt, you can see the threads in it) is the outermost bolt for the "big" radiator. That is far beyond the cutout in the core support.
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a radiator that much wider than the opening just does not make sense - the way things work I wonder if the cooling engineers at GM intended for the radiator support to have a larger cutout but somewhere along the line someone made a value engineering decision and cut the support redesign out and figured it would be good enough (and/or did not have a clue about cooling) and let the warranty dept deal with the failures

also, is that a cummins I6 in a K5?
 
JoshHefnerX said:
That's temporary. It will help for short bursts of heat and may stabilize the temps, but if the heat can't be removed, it's going to heat up the entire mass.
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That is what I don't understand. They have the grill area and there is room on the radiator support to widen the opening (relocate overflow can, vapor can, and cold air intake). They made the wider radiator and added the bolts holes for the brackets. They could have made the 'real' solution and widened the opening but instead they went for the 'short burst' solution.

Now that I am thinking about it - with a welder, a cutoff wheel, and a few feet of flat bar; I bet I could redesign and widen that opening in less than 30 minutes.
 
Just be sure to strengthen anything you remove. That does hold a lot of stuff together.
 
Undoubtedly a "temporary" solution, at least with any sort of additional capacity they could easily add. Extra coolant adds heat capacity, at some point with enough coolant you'd eliminate the problem completely, likely in unrealistic quantities. But the difference in that huge radiator vs. the smaller ones is likely on order of 1-2 gallons at most.

You could accomplish the same thing GM did without doing anything but adding coolant capacity somewhere, for probably less expense. Those huge radiators are pricey and only going to get harder to source. Plus they come with added problems of fan shroud, fitment of other components, etc.

No idea about engine on that pic, I just googled CUCV radiator to try and find a pic of the core support in use with the huge radiator, which I couldn't.

We all probably need to remember that we ask a LOT more out of our vehicles today than back when they were designed. Our vehicle expectations are different than our parents and grandparents. There are still signs out this way on some hills that say "Turn AC off to prevent overheating", which very few would find acceptable with a new vehicle. Look at what we tow today and annual mileage driven now vs. 1970's and 80's. We're demanding more than what the GM engineers were probably worried about the vehicles being subjected to.

I don't think the core support design was all about saving money vs. radiator performance. I'd expect it's construction was based on strength, as the supports in the core support are integrated into how the front clip mounts to the frame.
 
dyeager535 said:
We all probably need to remember that we ask a LOT more out of our vehicles today than back when they were designed. Our vehicle expectations are different than our parents and grandparents.
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When I was a kid my grandparents had a really old jeep that they used as a ranch vehicle. It was a 1967 CJ5 and this was 1987. My blazer is over 40 years old and it is my main vehicle. So I hear you on difference in expectations.
 
I also don't say that meaning we should ACCEPT what we consider substandard performance, simply that we are having to come up with solutions to problems that GM's engineers didn't have to deal with. We've got almost 40 years of tech and hindsight on our side. If it came off as an insult of you, I apologize, totally not my intent.

We can make a large number of modifications and add modern convenience and tech to bring these trucks *closer* to what you can buy today.
 
dyeager535 said:
I also don't say that meaning we should ACCEPT what we consider substandard performance, simply that we are having to come up with solutions to problems that GM's engineers didn't have to deal with. We've got almost 40 years of tech and hindsight on our side.
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I completely agree with you and was adding to your point about expectations. Sorry if I sounded crabby.

The grandparents were really good about keeping things forever - they just thought a vehicle was worn out after 20 years and more or less unserviceable (grandpa was a flathead mechanic before the war). That CJ5 is still not old. They were always amazed I had taken their old K5 (20 years old then) and had it driving. I loaned it back to them for a month and after driving an escort grandma could not believe she used to drive the K5. My grandpa did not accept the GM engineering either - in the early '80s he put in a Buick v6 because he thought it would be better tech than the 350.

I hear your point, mechanically, the "40 years of tech and hindsight on our side" that the GM engineers did not have. Plus they never expected these to last more than 10 years nor to go more than 55 mph with 110HP on bias ply tires and maybe go down a few dirt fire roads. I expect my K5 to average 13mpg and be able to accelerate on 300HP all day long while going 75mph uphill on a 105 deg day with my hands off the wheel and stay in its own lane. Then, I want to drive up a creek bed over boulders without spinning a tire and after that through a foot of mud at 4,500 rpm spinning all four. All the while, I don't want my temperature to move more than five degrees. It never worked like that when it was new.

But because of knowledge sharing sites like CK5 and some aftermarket parts, it does (almost).
 
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