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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, 107 views)
File Type: jpg Rad outlets.jpg (471.6 KB, 102 views)
File Type: jpg Rad fillers and tubes.jpg (445.0 KB, 104 views)
File Type: jpg Rad isolators compared.jpg (339.2 KB, 104 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, 101 views)
File Type: jpg Rad outlet hose adapter.jpg (289.4 KB, 99 views)
File Type: jpg Rad lower hose adapted.jpg (410.1 KB, 101 views)
File Type: jpg Rad vent hose adapted.jpg (513.4 KB, 98 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, 101 views)
File Type: jpg Rad core supt modif 1.jpg (488.8 KB, 102 views)
File Type: jpg Rad core supt modif 2.jpg (402.1 KB, 101 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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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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Old 11-11-2017, 11:23 PM   #11
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All the electric fan people will tell you to replace the stock fan on the radiator side, as the work better on that side, but what I have found is that even the largest electric fans move much less air than the mechanical fans. I tried every electric fan I could find on my twin turbo 1970 Challenger, and none came close to keeping it cool. Put in a tight thermal clutch fan at the air conditioner fan speed (pulley selection) and the car never overheated after that.

I think they actually use electric fans in the 1500 vans, or did when it was available, but not the heavier ones. In my old 1996 Buick Roadmaster that weighs in at about 5000#, there are two big electric fans which do OK, but if the car had the trailer package, they put in one mechanical fan and big electric fan because the two electrics couldn't handle it. I think essentially all 3/4 ton and above come with mechanical fans, but may be wrong on that.

I have two of the highest output 16" Spal fans on ours and can tell you that they don't move as much air as the mechanical fan, especially when the thermal clutch in the fan is locked up. The radiator core is 34X17, so you are pretty much limited to two 16" fans max.

It will be interesting to see how it cools with the two electrics only, but my gut feel is that you will not have enough airflow to keep cool, especially since the trans cooler is still in the system and getting the hot trans fluid first.
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Old 11-12-2017, 12:14 AM   #12
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I, too, added two fans ahead of the radiator. Was disappointed I couldn't get them up against the radiator due to the trans cooler and didn't make a tight cowl due to the fabrication difficulty but going uphill in a Phoenix summer without a trailer I could stop the needle's climb.

With engine off a lot of air didn't seem to make it through the radiator and I thought I had wasted my time but engine on things seemed to work.
Harry 2003 C190P
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Old 11-12-2017, 02:55 AM   #13
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I, too, added two fans ahead of the radiator. Was disappointed I couldn't get them up against the radiator due to the trans cooler and didn't make a tight cowl due to the fabrication difficulty but going uphill in a Phoenix summer without a trailer I could stop the needle's climb.

With engine off a lot of air didn't seem to make it through the radiator and I thought I had wasted my time but engine on things seemed to work.
Harry 2003 C190P
Sounds familiar, but there is a way around a lot of it. On ours, I just put the fans tight up on the AC condenser, as the radiator is behind it, and then moved the trans cooler(s) to be to the front of fans and overlapping them. That way you get the cooler getting air sucked though it by the fan, and the fan is tight to the condenser so it pushes air through it better. No special ducting required and brackets for the cooler are really pretty simple.

The other thing that I have done that did seem to help was seal off the bypasses where the grille air can go around the radiator. There were a lot of them. Both sides, the bottom, and top all let a lot air that came in the radiator got wasted going around the radiator. I used masticated rubber sheet like is used for factory splash shields, easy to cut and fit and very durable. You can get it on ebay.

I think there are pix of both of these setups, so I will try to find them and get some links posted here.

Found this one

http://www.classbforum.com/forums/f8...hevy-6402.html

The cooler and fan orientation is still like shown, but the coolers are now both used to the trans, and the oil is back into the radiator.

Just found the original fan install that also covers sealing up the air bypasses and wheelwell splash areas that were fouling the radiator with slop.

http://www.classbforum.com/forums/f8...-fan-1991.html
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Old 11-12-2017, 04:55 PM   #14
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Mt 2007 Chevrolet Avalanche with a 5.3 V-8 has factory dual electric fans and it does great towing a medium sized load through the Colorado mountains as well as New Mexico in the summer.

I will try the shrouded dual fan setup and see how it performs.
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Old 11-12-2017, 05:22 PM   #15
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Mt 2007 Chevrolet Avalanche with a 5.3 V-8 has factory dual electric fans and it does great towing a medium sized load through the Colorado mountains as well as New Mexico in the summer.

I will try the shrouded dual fan setup and see how it performs.
I think in 2007 all the Avalanches were 1/2 ton, so that will make a difference, plus the pickup tend to have better radiators and also bigger engine compartments that allow much better airflow than a van.

Later versions of the same truck came with a 6.0 and 4L70e or 4L80e, I think, so looking at one of them in a 2500 or 3500 size would be more comparable to the van.

Can't hurt to give it a try, at least you are close to the mountains for testing, as long as the steep grades aren't snowed in and closed. My guess would be the bigger radiator would be a must with electric fans as the two core will require lower airflow for the same cooling. If there is a difference, it will be a low speed steep climbs, traffic with the AC on, etc, at speed the fans don't do much.
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Old 11-12-2017, 05:54 PM   #16
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yeah, I'm going to look hard at the bigger radiator - for the price there's really no reason not to do it.
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Old 11-12-2017, 07:05 PM   #17
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Do you have a link for the fans, it would be interesting to look up the specs for them, I think, for a lot of us.
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Old 11-13-2017, 10:43 AM   #18
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https://www.ebay.com/itm/CHEVY-EXPRE...gAAOxyRhBSxwqt

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Old 11-13-2017, 08:13 PM   #19
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Interesting looking fanset. From the specs on the FF Dynamics site it would 15" fans running at 18 amps (rated at 13.8 volts, it appears) and 3600 cfm.

Can't speak for these fans or manufacturer because I have never tested one, but have done just about all the major brands at one time or another.What I have found is that the sizes, and amps will likely be to spec, as long as you know what voltage they are using for the spec, as there doesn't seem to be much of a standard for the voltage. As far as the cfm is concerned, it, in most cases, has no relation to reality . Very few will ever give you a flow at pressure chart or graph, so they are using zero pressure on likely both sides, both of which never really happen in the real world, especially in a suction application where you will have a negative on the intake side and pressure on the output side. In a pusher especially, install, road speed can actually increase the inlet pressure, so that can subtract from the discharge pressure for reading the graph, so you see increased flow. These styles of fans drop flow very, very, quickly with inlet resistance or discharge back pressure.

For all of the above reasons, it has always been the most accurate for me to go by the amp draw, as long as you know they rated it and the airflow at the same pressures and voltage. 18-20 amps is pretty typical for the higher performance end of most brands, with many being 16" and some 15". On brands that make both curved and straight blade versions, the straight blades always have better airflow over curved, but are much noisier. Pushers will almost always have more flow than pullers. Similar designed fans with similar amps seem to perform very close the same.

So, for the same amp range, you have similar fans that run from 2000cfm to 3600cfm in the market. My guess, is that in practice, there will either be very little difference in performance or the 2000cfm one may even do better because it is straight blades vs most of the others that are curved. I don't say this is good or bad between brands, just that you need to throw out the cfm ratings in most cases.

In the case of the linked ones, it is hard to guess how things will go because the picture is not of a van install it appears, and they seem to use that pic for many different applications. I would certainly not be fond of the shroud design if that is what the van one looked like. It is too shallow to the radiator and not tapered to the fans, so won't pull from the entire radiator. The forced airflow when driving, which will be major part of the cooling air at highway speeds, will be impaired by the shallow shroud and the very wide blades used in the fans. IMO, any puller electric fan shroud should have flaps to let the pressurized speed driven air flow around the fans to help out. The problem with the electrics as a puller is that they don't speed up with the motor, so you don't get increased airflow capability to help the air go through even when they are running. The van setup may have the flaps and/or be deeper, but I don't the pic is of one.

The Chevies are highway speed/high load impaired, which can be caused by a couple of things. The first is radiator capacity, and the second is airflow. The fact that, on ours, we see an improvement in cooling with the fans on at highway speeds (50ish) would indicate a lack of airflow is at least part of it. There are lots of air bypasses from the grille area around the radiator, and there is very little room for the air to get out of the engine compartment, so you get backpressure that reduces airflow, and lose a lot of road forced air that goes around the radiator.

Even the best of fans can only do so much at highway speeds, as they don't move nearly as much air as the speed does, that leaves the bypasses, which you can address readily, and trying to get the air out of the engine compartment better, which is much tougher. A good test is to hold your hand at the final place the air comes out of the cooling area, which would normally be behind the fan or shroud, installed in the vehicle. If the air coming out doesn't feel like the air on your hand when you stick it flat out the window at 50mph, the electric fan is not really going to contribute at 50mph.

This leaves you to only the radiator to try to make major improvements, but the changes to the radiator need to take into account that your are dealing with lower airflow than most modern radiators like to have. The radiator in the vans might cool a pickup with a massive engine compartment and grille area fine, but not the van.

Large frontal area, wide fin spacing, single core radiators do really well at high airflows, don't get plugged as easily, and allow more air to go through the AC condenser at the same time. That is the style of the stock radiator with it's 15/16" or 1 1/6" core and 6 fins per inch.

Stacked multiple cores and tighter fin spacings tend to do better with low airflows, bu also contribute to them with higher resistance to airflow. Most of the old copper/brass radiators where this way, with very tight fin spacings and lots of core depth.

The Spectra radiator leans toward being better for low flow, but I don't know that it works out in the real world yet. It has two 1 1/16" stacked cores and 7 fins per inch spacing, so it should perform better with the lower airflow the vans seem to have. The junk yard radiator I also have is the same thickness but has even tighter fin spacing at 9 fins per inch.

It is likely that the larger capacity radiator will help the electric fans work OK, as it will cover the highway speed reduced airflow better, and the electrics will probably be OK at low speeds. I don't think the electrics would make it with the stock radiator, though. The big unknown is how much heat the transmission dumps into the radiator on various climbs. The latest information I have been able to find for our van would indicate that the torque converter will never be locked on a climb in 2nd or 3rd gear at under 50mph (even in tow/haul), so lots of heat to get rid of. The non high gear climbs are the ones that we have the highest temps on, typically 30-35mph in second or third gear. Between the reduced speed forced airflow reduction and and the converter unlocked, the trans can get hot and also then make the radiator run hot.

I think we all will be interested in how the bigger radiator, electric fans, trans still going into radiator, works out in tough conditions. It will be another data point in the list of combinations for improved cooling.
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