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Old 11-11-2017, 12:01 AM   #1
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Default Big radiator for later Chevies?

As many others have over the years, I have searched for a higher capacity radiator for the post 2003 Chevies many times without success.

As it turns out, there does appear to be a radiator that seems to fit the requirements and is nearly a drop in.

The actual application is for the previous generation Express van and before they switched to the 8.1 liter gas engine and still had the 7.4 liter. I think we never found it before, as we all were looking at small block stuff, and in those years the 5.7L radiator was 3" narrower than the current version. Odd part is that they used the width radiator as the new ones have for the diesel and the 7.4L. I used model year 1998 which is in the middle of the years.

It also appears that they carried over a lot of parts, and/or dimensions at the generation change in 2003. The mounting system (saddle) and shroud setup are nearly identical), and you could even put the old narrower 5.7 radiator in a newer Chevy, it appears, as well as the wider one, with just a shroud change and some baffles. The important part is that the saddle and top shroud (which holds the top saddle isolaters are sill sized to handle the two core radiator from the diesels and 7.4L engines, as well as the single core stock radiators we all have.

The differences between a stock 1 1/16" core radiator and the two core 2.125" core radiator are pretty easily handled, IMO. Of interest is that the two core also has tighter fin spacing at 7 fins/inch compared to 6 fins/inch for the stock radiator.

The lower radiator hose is the same diameter, but the new ones have a quick connect to the radiator and the older one is a normal hose barb connection.

The vent hose that goes into the radiator right below the radiator cap is not on the older style radiator, but they have a heater hose sized connection just a bit lower, so the size of the hose needs to be adapted.

The radiator cap is the two ear type that has been used for decades instead of the threaded cap on the newer radiators. Both use a non pressurized overflow tank which is a surprise because a lot of the 90s GM stuff used the pressurized overflow.

That is it for the differences that need to be handled to get twice as much core area as the stock radiator has. Of course, stacked cores like this are not as efficient as two single cores, but most would say they get over 50% more capacity out of them.

I personally have two aftermarket units of the old style radiators, and one looks like it would fit as above, and was just purchased from Spectra. The other was from a local junk yard that I got to see if it all would actually work out. It has a squarer tank on the driver side, so required a slight change to plastic core support. I don't think the Spectra would require it, but don't know for certain because I had already done the change to the core when I got it.

Here are the OEM and the Spectra side by side



The difference in the outlets



The different vent tube connections and radiator cap area



Here are the lower radiator saddle mount isolators I took out. The radiator just sits on them at the crimp between the core and the tanks. These were identical at one time, so obviously, the oil spilled from my several cooler experiments attacked them. One has grown over 3/8" from the oil and gotten very soft and sticky. It is nearly impossible to disconnect the coolers without the isolaters getting oily, so best to just buy two for the bottom, the tops survive fine and can be reused.

Attached Images
File Type: jpg Rad cores and inlets.jpg (461.8 KB, 86 views)
File Type: jpg Rad outlets.jpg (471.6 KB, 81 views)
File Type: jpg Rad fillers and tubes.jpg (445.0 KB, 83 views)
File Type: jpg Rad isolators compared.jpg (339.2 KB, 83 views)
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Old 11-11-2017, 12:12 AM   #2
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What is the Spectra part number if we chose to do this?

I can't pick it out of Spectra's website.

I have found adding electric fans helped, just an FYI.
Harry
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Old 11-11-2017, 12:21 AM   #3
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The install of the Spectra two core radiator was very straightforward, with exception of a Chevy specific PITA.

It is borderline impossible to get the upper shroud out without removing the both dipsticks and tubes, plus the oil fill tube. The problem is with the transmission dipstick/fill tube that can't be moved out of the way without taking it loose at the rear of the engine. This requires removing the doghouse, which means removing the passenger seat, the console, and both dash knee bolsters. Very stupid design IMO, and a PITA to do, for sure. If you don't remove the trans tube, you very, very, very, likely will bang up the fins on both radiator you take out and the one you put in. Even with it out, it is a good idea to tape cardboard over the core area to protect the fins as you put it in as the top shroud has lots of sharp corners that will hit. You don't have to remove the bottom shroud, just take out the two screws at the bottom from underneath, as it will move back far enough to change the radiator.

Here is the support at the rear of the engine that needs to be removed so you can slide the tube rearward.



The radiator hose is 1 9/16" ID, which is kind of an odd size, and it needed to be about 3" longer to reach the radiator after cutting off the QD. I couldn't find a local splice that size, so just made one out of 1.22", sched 40 aluminum pipe.



I got piece of 1 9/16" radiator hose and spiced it in with 3 constant force spring clamps.



I made a similar adapter for the vent to radiator out of 3/4" aluminum bar.



With the Spectra, I think that is about all that would be needed to be done to put in the big radiator. Everything else goes in just like stock.
Attached Images
File Type: jpg Dipstick in doghouse.jpg (545.2 KB, 81 views)
File Type: jpg Rad outlet hose adapter.jpg (289.4 KB, 79 views)
File Type: jpg Rad lower hose adapted.jpg (410.1 KB, 81 views)
File Type: jpg Rad vent hose adapted.jpg (513.4 KB, 77 views)
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Old 11-11-2017, 12:35 AM   #4
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A bonus is that the Spectra has a radiator drain that is accessible and by drilling a 5/8" hole through the core support can have a hose on it to drain the radiator without making a mess like you do taking off the QD on the existing radiators.

This is the drain hose. It comes out at the body mount on the driver side inline with driver side radiator end.



Here are a couple of pix of the core support mod that likely wouldn't be needed with the Spectra, but might with some other aftermarket brands. The area show in just inboard of the headlight and turnlamp bucket. The inside corner of the area was square and hit the squared off tank, so I just added angled supports and ground off the square corner. It is plastic so very easy to do.





I will get a parts list with part numbers in the next post.
Attached Images
File Type: jpg Rad drain hose.jpg (488.8 KB, 82 views)
File Type: jpg Rad core supt modif 1.jpg (488.8 KB, 83 views)
File Type: jpg Rad core supt modif 2.jpg (402.1 KB, 82 views)
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Old 11-11-2017, 12:51 AM   #5
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Here is the parts list for what I think most all would need to do the two core radiator swap. Of course while you are in there, you may want to replace the radiator and heater hoses, and the thermostat.

Radiator -- Spectra CU1787 More Information for SPECTRA PREMIUM/COOLING DEPOT CU1787

Radiator cap -- Gates 31523, or any other for 1998 with 7.4 engine. More Information for GATES 31523

Short piece of 1 9/16" radiator hose -- can usually find a cheap radiator hose at auto parts store and cut. I replaced my original hose and used a bit of it for the extension.

Short piece of 5/8" heater hose. I used a cutoff piece from the existing heater hoses that I replaced a while ago.

Two lower saddle mount isolators (one set) -- Dorman 926276 More Information for DORMAN 926276

One 1 9/16" hose splice -- Probably available, but I made mine. Aluminum or steel, don't recommend plastic. Could be pieced with hose barbs and coupling

One 5/8" hose to 3/8" hose spice adapter -- same as above about finding

Hose clamps for all the connections. I like the constant force spring style as they never come loose or leak. There is a reason OEMs like them. You can get all the sizes you need from McMaster Carr.
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Old 11-11-2017, 12:56 AM   #6
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Quote:
Originally Posted by hbn7hj View Post
What is the Spectra part number if we chose to do this?

I can't pick it out of Spectra's website.

I have found adding electric fans helped, just an FYI.
Harry
You got me too early parts list is now in a later post.

We have also had electric fans, two 2400 cfm Spal units that move a lot of air, but we still would get hotter than I like sometimes. Lower gears and very steep climbs hurt us the most. I just don't like it to run very far off thermostat for water or trans.

I have no idea if this will fix everything for everybody, but I think it will likely make both the water and the trans run cooler, as the radiator should not be maxed out all the time on climbs. I am a thousand miles away from any real climbs, so it will be a while before I get a chance to really see how much good it does.
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Old 11-11-2017, 02:35 AM   #7
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We are in Phoenix and all northbound roads have steep climbs. Add a 14ft. enclosed trailer to the mix and it is a very difficult situation, even in the spring and fall, impossible in summer.

I, too, spent some time looking for a dual core radiator with no success so thank you! It isn't a cure all but added to electric fans it should help.

Rock Auto had the radiator for around $160.
Harry
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Old 11-11-2017, 07:01 PM   #8
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Very good info- thanks for posting it up!

I may upgrade mine to this radiator when I install the dual elec fans soon as I have to remove the radiator to install the fans, so it would be the opportune time to upgrade.

Can the lower radiator hose be installed without the pipe, maybe use the version of the hose for the earlier model vans?
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Old 11-11-2017, 08:03 PM   #9
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Originally Posted by Hondo View Post
Very good info- thanks for posting it up!

I may upgrade mine to this radiator when I install the dual elec fans soon as I have to remove the radiator to install the fans, so it would be the opportune time to upgrade.

Can the lower radiator hose be installed without the pipe, maybe use the version of the hose for the earlier model vans?
I didn't look at the hose from the old 5.7 or 7.4 to see if they would work, as it is likely they won't because those engines had the normal thermostat and water pump setups, and there was plenty of straight section to splice into the stock hose. You would have to get them and try, I think, as at least on ours, the area out of the thermostat area and around the curve has to be very close to identical to clear everything. Only the last 6 inches to radiator has much room. It is certainly possible one of the two, most likely the 7.4 one I think because the 5.7 radiator was narrower. But of course the 7.4 engine was wider and longer, so that could make a difference. I do think all three had all the same 1 9/16" hose size, though.

You should not need to remove the radiator to install the fans, I think, as the shroud is two pieces. Just remove the top and you will have access. This is assuming you use supports that go back to the outside framework of the core support so you don't need to put the through the fin mounting on, which I wouldn't recommend anyway, as they can damage the radiator over time from bouncing and vibration. Most of us have left the Chevy clutch fan in place and added the electrics on the outide of the radiator. Easy to do as the grill comes out easily, and you also get the benefit of increasing the airflow directly to the trans cooler.
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Old 11-11-2017, 09:40 PM   #10
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The fan kit has shrouds and they recommend removing the radiator in order to install them with their hardware...I'll look really close to it before removing anything. This dual fan kit is installed after removing and in the place of the shroud & clutch fan, not an addition.
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