[GMCnet] Replacement Radiator 4-row versus 2?

[Jess Bressi]

Greetings all. I have a Cortez, the Steel precursor to a GMC. Same drivetrain, 455 Olds, Turbo 425, 3.70 final Drive from Applied, etc. Need a new
radiator as a new Modine core appears to be made of unobtanium and a custom replacement core is very pricey. Jim Bounds replacement won't fit/work
without major new fabrication. I also use the Applied/Tom Pryor MB electronic fan clutch fan and I'd like to keep that. I've seen that some folks
are adopting CarQuest Part No. 733730 aluminum radiators from GM small trucks but all the one's I've found are 2-row. Is anyone using a 4-row version
of the same radiator? If not, is the 2-row sufficient. Thanks in advance for your consideration.
--
Jess Bressi
Orange County, CA
1972 and 1974 Cortez's
455's/3.70's/Patterson Q-Jets
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[Jess Bressi]

Correction, part no 433730.

[Mark Sawyer]

Not sure if the Cortez is the same, but on GMC motorhomes, the rad has 2 oil coolers present... One for the engine oil, one for the trans. At the
very least, you may need to add an external cooler as I only see one oil cooler on 433730...

Also, on the GMC at least, the aluminum radiators available are also 2 core, but the dimensions are different. 433730 is 28x19"... GMCs are 28X23...
Whether this makes a difference for you I guess would depend on the climate where you live, if you plan on towing, how much air you are able to move
through the core, etc...
--
Mark S. '73 Painted Desert,
Manny 1 Ton Front End,
Howell Injection,
Leigh Harrison 4bag and Rear Brakes,
Fort Worth, TX

[John R. Lebetski]

Aluminum is less efficient at heat transfer, but tube sizes are deeper as they are stronger so they can be, giving better surface area per row
So you can’t compare rows between copper brass and aluminum as row for row.
--
John Lebetski
Woodstock, IL
77 Eleganza II

[John R. Lebetski]

See if this helps explain https://www.dewitts.com/blogs/news/14759109-why-aluminum-radiators-cool-better

--
John Lebetski
Woodstock, IL
77 Eleganza II

[Greg Crawford]

Just for comparison sake, I just pulled the factory radiator out of my 77 Royale this week. A local radiator shop I took it to quoted $800-1000 to
re-core it. Really nice guy, gave me several minutes of his time, and we discussed aluminum vs. brass/copper radiators. As you may imagine, he was not
a fan of the aluminum radiators because in his opinion they don't last, and can almost never be repaired, especially with the plastic tanks.

I drove a hundred miles to another reputable shop that I had previously contacted. Their quote was $600-700 for an 18 fin per inch, four row core with
my factory tanks. We talked about aluminum. He said "If you are going to keep it, put in the brass/copper. If you are going to sell it, put in the
aluminum one." Now I had asked for a quote from this same shop in November. It was $500-600 then. He said things had gone up that much since then. I
should have taken it to him in November.

I opted for the new core with my old tanks.

I would not want the two row radiator.
--
Greg Crawford
KM4ZCR
Knoxville, TN

"Ruby Sue"
1977 Royale
Rear Bath
403 Engine
American Eagle Wheels
Early Version Alex Sirum Quad bags

[David H. Jarvis]

It wasn't that long ago that Bounds had nothing good to say about aluminum rads.

[Greg Crawford]

Sorry to take so long to answer.

I removed the radiator in about two hours. However, I did as many have done, and cut the radiator support about 4 inches up from the bottom on each
side, while supporting the assembly with a floor jack. This enables one to drop the radiator straight down, then tilt the bottom toward the front of
the coach, and take it out. It is heavy, so help would be appreciated, although I managed by myself.

I then welded 1 x 1 x 1/8" angle iron pieces, 4 inches long, to each end of the cut off section. Holes were bored in all four pieces of the angle iron
to receive 5/16" x 1" bolts. I tack welded the bolt heads in the upper pieces so I wouldn't have to use a wrench to hold them. I then bolted the upper
pieces to the lower ones, which had already been welded to the cut off section. I secured the assembly to the part of the radiator bracket remaining
in the coach with welder's vise grips. This ensured proper alignment of all pieces. I then welded the top angles to the radiator bracket, and unbolted
the lower section.
Now I spend a lot of time wire brushing, cleaning, and repainting every part I remove, so my installation time will be much longer than is strictly
necessary.
I am replacing all coolant hoses, belts, oil cooler lines, transmission lines, power steering hoses, front motor mount, water pump, fuel pump, and
timing chain. My timing chain was extremely loose, and at 67,000 miles. You can remove the fuel pump and check the chain for looseness, but I would
recommend putting a socket on the crank bolt and moving the crank a little each way to make sure you are feeling the true slack.
My radiator is not yet done, so I have not yet reinstalled it. I would estimate about two hours to put it back, and another little bit to refill
all fluids, install the fan, belts, etc.
This was most certainly more than you wanted to read, but there it is.

--
Greg Crawford
KM4ZCR
Knoxville, TN

"Ruby Sue"
1977 Royale
Rear Bath
403 Engine
American Eagle Wheels
Early Version Alex Sirum Quad bags

[Robert Mueller]

I did a quick Google search on the thermal conductivity of metal and this came up:

Common metals ranked by thermal conductivity
Rank Metal Thermal Conductivity [BTU/(hr·ft⋅°F)]
1 Copper 223
2 Aluminum 118
3 Brass 64
4 Steel 17
5 Bronze 15

Is the GMC radiator core copper? I vaguely remember seeing one stripped and it wasn't copper colored. Having noted that my grey cells aren't what they
used to be. :)
--
Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426

[Emery Stora via Gmclist]

Hi Rob
I don’t think our radiators would be copper because they would not have the strength needed. Think of a sword made from copper. It would easily bend and not be a good weapon. However if you add zinc or other metals to the copper you create brass or bronze. Thus the Bronze Age with strong weapons.
Bronze is an alloy of copper which would give it strength. Often it is 30% or so zinc added to the copper. Other metals are often added to give other properties. But, as you can see from your chart the thermal conductivity is much lower for bronze. Brass would better but not as good as aluminum.

Emery Stora

> On May 8, 2021, at 7:41 PM, Robert Mueller <robmu...@iinet.net.au> wrote:
>
> I did a quick Google search on the thermal conductivity of metal and this came up:

[Robert Mueller]

Emery,

Agreed, I reckon it's an alloy of copper and zinc which gives it the gold color.

I'd GUESS that the aluminum radiator would have better thermal conductivity.

BTW ALL Hamilton Standard commercial aircraft air conditioning systems have aluminum heat exchangers except for the Concorde it was titanium.

[Johnny Bridges via Gmclist]

I'm with Greg, here in the southeast the 2 row would be marginal at best. I've had two recored, price went fro 350 to 500, shop told me up front the
price of materials had nearly doubled in the intervening two years.


--johnny
--
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell

[Jim Kanomata]

We sell more Al radiators than others and know it is not the material, but
what they do to it to increase surface area of not only the fluid side but
the air side.
Also the Fluid tubes are thicker to last longer and it also now has an
Anode to cut down on electrolysis.
The design has been used and proven in lot of applications, so it is not
new.

--
Jim Kanomata
Applied/GMC, Newark,CA
ji...@appliedairfilters.com
http://www.gmcrvparts.com
1-800-752-7502