Want More
Cooling?
What are
the Advantages & Disadvantages
Of Upgrading
your Model A Ford Radiator?
By:
Andy Wiedeman
Member of the Rocky Mountain A’s of
Please use the
following Menu to Navigate through the paper.
Clicking on a Topic will take you to that chapter and/or paragraph. Use your “Back Button” to return to the menu.
Engineering
and Theory of the Model A Radiator
Improvements in Cooling
for the 1928 – 1929 Model A
1928
– 1929 Authentic Restoration Cars
1928
– 1929 Touring Restoration Cars
Improvements in Cooling
for the 1930 – 1931 Model A
1930
– 1931 Authentic Restoration Cars
1930
– 1931 Touring Restoration Cars
Cooling
Capacity of the Radiator
Model
A Ford Radiator Specifications
Standard Radiator
Specifications vs. Availability 1928 - 1929
Standard Radiator
Specifications vs. Availability 1930 - 1931
Heavy Duty Radiator
Availability – Not Show Quality
Comparison of Restoration
Radiators for the 1928 – 1929 Model Years
Comparison of Restoration
Radiators for the 1930 – 1931 Model Years
Test
to see if you need a new Radiator
What
is Available – Research Details
Marketing Information
provided on the Brassworks website.
“Authentic” original
radiator design
The “Ultimate” 4 core
radiator
Installation
of a Modified Radiator with a 4 Row Tube Core.
Installation of a
Replacement Radiator
The use of an actual AA
Truck 4 Row Radiator
The use of a Bert’s Model
A Center 4 Row Radiator
Many thanks to Steve Becker at
Bert’s Model A Center for editing and information.
Introduction
Many Model A Owners want to get more cooling for climbing hills, driving in
the desert and other places where their Model A tends to get too hot,
especially in the summer. In my case,
after any tour that I went on, there was still a 7 mile uphill grind out of
Indeed, here in high altitude
The largest variation in the ability to purchase a replacement radiator which is the same as or close to the original Ford version is in the 1928 to 1929 model years. In these years the radiators were 4 row designs for 1928 and either 4 or 5 row designs for 1929 depending on the manufacturer of the radiator. Currently, after comparing 5 mail order supply houses, we find that there are not any 4 or 5 core radiators available on the market. It seems that the radiators are all 3 row designs. For 1930 and 1931 it is possible to get an “almost” show quality radiator
This paper explores the design and theory of the Model A radiator, various possibilities for increasing cooling in the Model A, help in choosing the best radiator for your car, what it will cost, and the problems you may get into.
The bottom line is that a 4 core radiator, built on the upper and lower tanks
with the original side rails of either an original 3 core or a replacement 3
core (the most common radiator found in restored Model A’s) will provide superior cooling compared to Model A’s that have
earlier “replacement” 3 core radiators.
If you have a 1928/29 with the old 4 row round tube radiators, you will
see an enormous improvement. The
improvement for a 1930/31 is less but still will nearly double the cooling
capacity of a 3 row radiator. The only known vendor supplying this amazing
cooler is Bert’s Model A in
There is considerable confusion as to the original designs as to how many
tubes, and how many fins were in the original Model A. However, the consensus is consistent, the
original 3 core flat tube radiator for the 1930/31 was adequate for cooling the
Model A except high altitude conditions such as here in
Engineering and Theory of the Model A Radiator
The Model A radiator was based on 30 years of radiator design technology prior to 1928. The design for the early 28 – 29 models changed very little from prior Model T round tube radiators. The initial 1928 Model A Fords used the round tube radiator design pirated from the Model T, however increasing the number of tubes, the number of rows from 3 to 4, and the radiator size. These radiators were manufactured by Ford. In 1929 Ford introduced 2 more manufacturers of radiators, Flintlock and McCord, the radiators from these manufacturers were also 4 row round tube designs, but in the case of the McCord radiator it had another row of tubes bringing the total to 5 rows. By late 1929, it became evident to Ford engineering that improvements in the radiator, were required. Ford then introduced a more efficient flat tube radiator design from 1930 to the end of production. The basic change in engineering that Ford implemented was the use of angled flattened tubes to direct the air flow past tubes with a higher ratio of tube to air flow exposure (more on this later on). This more efficient radiator allowed Ford to reduce the number of tubes in the radiator from 4 to 3.
The radiator principle for both the 1928/29 and the 1930/31 designs are based on what is called a “Compact Fin-Tube Heat Exchanger”. It implements a two fluid heat exchange aided by radiating fins, the radiator is constructed of vertical brass tubes carrying the water, which exchanges its latent heat with air flowing over brass radiating fins arranged horizontally and brazed to the brass tubes. The cooling principle requires the ambient temperature air to flow at high speed over the cooling fins. As long as the Model A is moving in excess of 10 to 15 mph, this requirement is satisfied. When the car is sitting still, or moving slowly, it is necessary to externally cause air to flow over the fins. This is the purpose of having a fan that will pull the ambient temperature air through the radiator, and expel it backwards past the engine. The radiator is constructed as shown below.
The variation in design between the 1928/29 model years and the 1930/31 model years, while considerable both use the same principle. The design change between these two model year versions yielded a much higher efficient radiator for the 1930/31 versions. Two changes were implemented at the same time. Firstly, as shown below the tube configuration was changed from a round seamed tube, to a flattened tube. Additionally, the radiator was lengthened by over 2 inches. Secondly, the flattened tubes were angled slightly to improve air flow streamlining.
Together, these two changes in tube and orientation configuration increased the tube area exposed to the air flow by 61% per tube. Shown below is the improved air flow.
.
The increased streamlining of the air flow, and the orientation of the tubes causes more exposure of the latent heat in the tube to radiate to the air stream, while also improving the conduction from the tube to the fin. The inefficient turbulent flow of air around the old 1928/29 round tubes was virtually eliminated. In 1931, the front edge of the fins on the improved radiator were dimpled slightly to break up the laminar flow slightly, since the 1930 radiator air flow was almost too good.
The number of rows of tubes containing water give the name 3, 4 and 5 “core” radiator to the various types available on the market for restoring a Model A. In Model A vernacular row and core, when referring to radiators are used interchangeably. Today, the original 1928/29 4 row round tube radiators, and the McCord 5 core radiator with 87 round tubes are no longer available. However, various mail order companies offer new and rebuilt 3 row radiators both in round and flat tube designs. Bert’s Model A offers a rebuilt 4 core radiator with flat tubes.
In both the 1928/29 round tube version, and the 1930/31 flat tube versions the rows of tubes are staggered, and for 1930/31 models angled to the air flow, to increase heat transfer directly from the tubes to the air. The Model A Ford has a total fin area of approximately 9,500 to 17,000 square inches (depending on the number of fins per inch and core thickness in the radiator) of fins exposed to the air flow through the radiator. This large heat dissipating surface area is compared to the approximately 1,500 square inches of tubes (for a 4 row 1928/29 radiator) to 3,700 (for a 4 row 1930/31 radiator) exposed to the air flow. This means that the primary means of cooling is conduction from the tubes to the fins, and then radiation from the fins to the air. Secondary cooling is provided by direct radiation from the tubes to the air stream.
The heat exchange mechanism is shown below (the flat tube is shown, however, the round tube heat exchange is similar).
The brass tubes are brazed to the fin which is manufactured of thin brass. The brass fin is a good conductor and pulls the heat from the tube and exposes it to the air flowing past the fin. Whilst, there is some heat transfer directly from the tubes to the air, the temperature drop in the water is highly proportional to the total area of the fins which are exposed to the air flowing past them.
There are three dominant design parameters which control the efficiency, and therefore, the ability of the radiator to cool the Model A engine. In order of influence on cooling, these are the total area of the fins exposed to the air flow, the configuration of the tubes (flat is much better than round), and the total number of tubes exposed to the air flow. To determine what your Model A’s radiator design is based on, measure 2 inches on the exterior of your radiator core and count the horizontal fins in this measurement. The number of fins per inch is then the number counted divided by 2. You can get the tube configuration and number of rows by manually viewing the interior of the core with a flashlite.
Improvements in Cooling for the 1928 – 1929 Model A
There are a wide variety of options for improving the quality of cooling for the 1928/29 Model A Ford. The original design, based on the round tube 6 fin per inch standard used on the Model T was not an efficient design. Therefore, there are three possibilities for improving the cooling capacity. The option that you choose, will depend upon your desired use for your Model A. To see a side by side comparison refer to the chapter on Comparing the Radiators.
1928 – 1929 Show Cars
Those owners wanting to have a “SHOW” car, judged for accuracy of restoration, have no real possibility of improving the cooling capacity. In fact, there are no replacement radiators available which are made to the original design standard. Owners desiring to restore a 1928 car to show will need to seek out a 4 row, 6 fin per inch radiator with 94 round seamed tubes and have it carefully rebuilt. Owners of 1929 cars can choose to use the 4 row 94 tube, 4 row 100 tube, or the 5 row 87 tube radiator. These radiators all have the same performance.
1928 – 1929 Authentic Restoration Cars
If you do not plan to enter “fine point judging” but still want to have a near authentic Model A, you have some options. Replacement radiators with the round tubes, used on the 1928 and 1929 are available from Bratton’s and The BrassWorks. The Bratton design uses 5 ½ fins per inch and has a slight reduction in performance relative to the original Ford design. The BrassWorks “Almost Show” radiator has the same performance as the original Ford design but has 3 rows not 4. The BrassWorks offers a 10 fin per inch “heavy duty” radiator with round tubes. This radiator is about 65% more efficient.
1928 – 1929 Touring Restoration Cars
If you plan to tour your car, and/or want much more cooling, your choice is simple. There are radiators manufactured for the 1928 – 1929 Model A that are based upon the more efficient 1930 – 1931 flat tube radiator design. These radiators are supplied either as 5 ½ fin per inch “Standard” replacement radiators, or 8 fins per inch “Heavy Duty” replacement radiators. Choosing this option will provide you with 63% or up to 95% more cooling. If you want the “Ultimate” touring radiator choose the Bert’s Model A 4 row, flat tube, 8 fins per inch radiator. This radiator will provide you with nearly 4 times the cooling capacity of the original Model A Ford, and is double the performance of the “Heavy Duty” flat tube replacement radiator.
Improvements in Cooling for the 1930 – 1931 Model A
Improvements to the cooling performance for the 1930 – 1931 Model A are more restrained since Ford had improved the cooling performance by adding the flat tubes and improved the air flow for these model years. However, there is still some improvements that can be achieved, by using a higher fin per inch count, and increasing the number of rows (thus the number of tubes) in the radiator core. The width and length of the radiator is constrained by the mechanical design of the hood, fenders, and engine placement, so there is little room for improvement for the 1930/31 Model A using the flat tube design beyond 4 rows. What is highly variable is the number of horizontal fins that can be brazed to the tubes. The original Model A sported 6 fins per inch, constrained by the manufacturing techniques of the day. Later replacement radiators incorporated 3 rows of tubes with 5 ½ fins per inch. Today “heavy duty” replacement radiators with 8 fins per inch are commonplace in the Model A and the BrassWorks radiator company, makes a “new” radiator with 10 fins per inch. The AA Truck radiator from the mid 1930 model year on, used 4 rows of tubes with a thicker core. Whilst the AA Truck radiator side rails are wider, and cannot be easily used on a car, Bert’s Model A offers a 4 core radiator built from a car radiator which can be used without modification.
The advantage of the 4 core radiator compared to the other types is easily discerned. The advantage comes from 2 sources. Firstly the area of the fins is expanded due to adding thickness to the core in order to have room for the additional row of tubes. This increases the total surface area from 13,500 square inches in a typical replacement 3 core radiator to 17,300 square inches, a 28% increase in radiation area. Furthermore, the tube direct radiation area exposed to the air flow is increased from 4000 to 5400 square inches or another 35%. A comparison of the performance of these radiators is shown in the Chapter on Comparing the Radiators.
Your choices for restoration are easier for the 1930 – 1931 Model A than the ‘28/29 model years.
1930 – 1931 Show Cars
Since the original 1930 – 1931 radiators were 3 row, 6 fin per inch designs, and were replicated by replacement radiator manufacturers after 1931 and still are available today. Your choices are wider than the ‘28/29 models, since 6 fin per inch radiators are available from several mail order suppliers. However, there will be no improvement over the original design for cooling.
1930 – 1931 Authentic Restoration Cars
If you want a car that is more authentic, but will not be showing the car in “fine point judging” you can improve the cooling capacity of the Model A, by increasing the number of fins per inch in the radiator, while keeping the 3 row design. Several mail order companies, and the BrassWorks provide “Heavy Duty” replacement radiators with 8 and 10 fins per inch. These radiators will provide a 25% to 60% improvement in cooling depending on the number of fins per inch. Beware of the 5 ½ fin per inch replacement “standard” radiators on the market. While these radiators are cheap, they are also 15% less efficient.
1930 – 1931 Touring Restoration Cars
For the “Ultimate” cooling
performance, Bert’s Model A in
Cooling Capacity of the Radiator
The cooling capacity of the Model A Ford radiator is sized to prevent the
cooling water from flashing into steam by designing the radiator to operate with
the engine outlet temperature normally at about 170 degrees F. The radiator design is built upon an ambient
temperature for boiling of the water at about 212 degrees F. This temperature differential of 42 degrees
allows for operating conditions to vary as the car is driven. Since we drive and tour our Model A’s in
In terms of cooling capacity increases the following table shows what you can do by changing the radiator. The table is arranged in columns with increased cooling as you go down the table. The cooling capacity estimate is based on using percentage increases in the number of tubes and the number of fins per inch. In the Ford radiator the water is in contact with the tubes that run from top to bottom of the radiator. The tubes, being made from brass, conduct heat away from the water. To increase the capacity for the tubes to radiate the heat from the water (which enters the radiator at about 180 deg F.) to the air at ambient temperature (typically 0 deg to 100 deg F) flowing through the radiator fins are soldered to the tubes forming a “core”. The heat dissipation is primarily proportional to the area of the fins, and secondarily to the number of tubes. To calculate the efficiency of heat dissipation for purposes of estimating the amount of increase of cooling capacity of one type of fin and tube radiator of a given total air flow area to another is a study in thermodynamics and involves the flow of water through the radiator at a given engine RPM combined with the speed of the vehicle and the air flow through the radiator core, the air temperature at the time of the calculation and a myriad of other factors. For purposes of simplification and obtaining a relative idea of the increased cooling between radiator types it is not necessary to calculate the absolute temperature reduction, but it is only necessary to compare the area of the fins and the tubes from one design to another.
Relative Cooling Capacity Calculation:
Cooling Capacity [Replacement Radiators]
Cooling Capacity [Relative] = ---------------------------------------------
Cooling Capacity [Original
Ford Radiator]
Where:
(1) Cooling Capacity = Area[Radiating Fin] + Area[Total Tubes] + Air Flow Efficiency
For this paper we set Air Flow Efficiency to Zero … therefore:
(2) Cooling Capacity = Area[Radiating Fin] + Area[Total Tubes]
Model A Ford Radiator Specifications
The available literature is confusing to the reader trying to figure out what the “real” story is about radiator design specifications. Probably the best source is the MAFCA judging standards book. When reading the other books and leafing through various mail order parts catalogs it is easy to get confused between designs, performance, and “show quality” radiators. In this paper I try to unravel this mystery by listing what the various specifications quoting sources have to say.
The MAFCA Judging Standards show the following chart to specify the configurations.
The standard shown in the diagram above provides information for the following specifications. The April 1930 service bulletin says “most replacement radiators have the 5 ½ fins per inch configuration
Radiator Specifications
|
Source |
Radiator Type |
Model
Yr |
Num |
Type
Tube |
Total
Tubes |
Fins/ |
Total Fins |
Comments by Source |
|
MAFCA |
“Original” |
1928/29 |
4 |
Rnd |
94 |
? |
? |
Ford Mfg |
|
1929 |
4 |
Rnd |
100 |
? |
? |
Flintlock Mfg |
||
|
1929 |
5 |
Rnd |
87 |
? |
? |
McCord Mfg |
||
|
1930 |
3 |
Flat |
102 |
? |
? |
Ford |
||
|
1931 |
3 |
Flat |
102 |
? |
? |
Ford |
||
|
Les Andrews |
Specification |
1928 |
4 |
Rnd |
94 |
? |
? |
¼” Diameter |
|
1929 |
4 or
5 |
Rnd |
100 |
? |
? |
100 Flintlock 4 row |
||
|
1930/31 |
3 |
Flat |
102 |
? |
? |
5/32 x 1/2 “ |
||
|
Mike’s Parts |
Specification |
1928/29 |
3 |
Flat |
101 |
5 |
98 |