Feb. 2018 - Preparations for an improved cooling package.
Improving your radiator.
There are 4 options -.
1. Re-core your original brass-copper radiator.
2. Buy a new original appearance brass-copper replacement.
3. Buy a new original appearance aluminium replacement.
4. Buy a new aluminium radiator which fits but has a different appearance.
All four options are capable of improved cooling and a decision needs to be made as to which is the best option for
your truck. If your truck is completely original you may decide not to change the radiator at all especially if you are
not experiencing any overheating problems, however, if you have a modified truck, maybe running a V8 then this
web page is designed to provide advice on the best way to improve the cooling systems in your truck.
We will consider, radiators, fans, fan shrouds and transmission coolers. Lets look at the options -
1. Re-core your original radiator. I discounted this option for several reasons, some of which will become apparent
later, however, to do the job well is expensive. You need to find a good company who can put a new efficient brass
copper core into your radiator and my checks led me to the conclusion the total cost could exceed £500 ($650) for
a good job. In addition, the truck is off the road while it is being done. Finally you can't claw back some of the
money from selling your original radiator as it is needed to be modified. Remember, if you buy a new radiator,
there will be plenty of people who own a completely original truck will want to buy your original radiator.
2. A new original appearance brass-copper radiator is a very good idea and this will be considered in the next section.
3. A new aluminium radiator which fits but has a different appearance. There will be many people who choose this
option as the exact shape of the top of the radiator will not be important to them. This will be the case when
there are many visual modifications to the truck. The aim of this project is to keep as much of the original
appearance as possible unless there is a good reason to change it on either safety, appearance, comfort or
performance grounds. (But there needs to be a good reason.) Since it is possible to buy a high performance
radiator which looks the same as the original radiator, option "3" was not considered.
4. A new original appearance aluminium radiator is a very good idea and this will be considered in the next section.
Comparing copper-brass with aluminium. Original appearance.
An original appearance radiator is shown above.
When all is considered the choice between "2" and "4" above is a close call and there is little difference in performance.
To improve performance in brass-copper a 4-row radiator is possible. This will improve the cooling as there are
more tubes and more cooling fins. The disadvantage is that it is quite heavy and can be expensive. A typical
4-row original appearance radiator weighs about 80 pounds (36Kg) and costs $500 - $600.
It is, however, possible to buy a quality 2-row original appearance aluminium radiator with a similar performance
to a 4-row copper-brass radiator for about $220. It is also considerably lighter at about 30 pounds or 16Kg.
The problem with aluminium radiators is that some companies who make them use a technique which is not very
efficient or ideal. This is almost always reflected in a lower price. The most efficient aluminium radiators use 1"
diameter tubes and if the tubes are less than that they will not be as efficient. Also note they may quote 3-rows
and again it is likely that the radiator will not be as efficient as a well designed 2-row radiator. The most
efficient (at heat transfer) radiator which will fit the truck uses two 1" tubes which are "shaped" "plate tubes"
for maximum surface area for the fluid going through them. Circular tubes are not as efficient. Many cheaper
radiators use circular tubes. To fit 3 x 1" rows into a radiator, these manufacturers would almost certainly
have to use circular tubes. 3-rows of circular tubes will not be as efficient as 2-rows of 1" shaped plate tubes.
Copper-brass radiators, due to the materials used, have tubes which are much narrower. Narrower tubes are not as
efficient, however, 4-rows can make up for that, unfortunately by the time the air gets through the first two rows,
it is quite hot and so the next 2-rows will be less effective at cooling. The efficiency of a good 4-row copper
brass radiator is similar to the efficiency of a good 2-row aluminium radiator which uses 1" shaped plate tubes.
At this point in my considerations I decided to read reviews of many radiators online. It soon became apparent
That whether you bought a cheap radiator from ebay (say $150), or a more expensive radiator from ebay (say $220)
or expensive radiators from the bigger well established companies online, $600 - £700 or $800 + there were many
people complaining about failed new radiators and failed replacement radiators for new radiators which had failed.
It was at this point I decided not to go ahead with any of the 4 options for the time being and to go for a
5th Option. I have a perfectly good original copper brass radiator and I will build a good shroud
for my existing excellent Spal fan.
Using a shroud.
There are pros and cons to using a shroud. If you don't use one, at higher speeds the air flows through the
whole radiator and this provides better cooling, however, it is at low speeds, bumper to bumper traffic,
slow manoeuvring etc, when the most heat builds up, in these circumstances, the fan is much more
effective if there is a shroud between it and the radiator. This is because -
The fan is pulling air through all of the radiator and not just part of it.
The fan creates a low pressure area (partial vacuum) between itself and the whole of the radiator
One effect is rarely considered - without a shroud, the fan is effectively "short circuited" at it's edges.
What this means is that instead of pulling air through the radiator, it also pulls air from behind itself
around it's edges. This is even the case if it is an electric fan and it is up against the radiator as outside
of it's circumference, it will not only be pulling the air in front of it, it will also be pulling heated
air through the radiator in the reverse direction (from behind the radiator) and then back through the radiator
and through the fan. This again is less efficient. On balance, if your new radiator is more efficient anyway,
the smaller amount of "ram air" going through the radiator at high speed due to the shroud should not be an
issue. Also note manufactures use shrouds in new cars for a very good reason. They are efficient
at low speeds when the most cooling is needed.
Using a shroud with flaps.
"Spal" make shroud flaps. They are less than $1.50 each and probably 4 of them will be needed.
Flaps open at high speed due to the force of the ram air coming into the front of your vehicle. At slower
speeds (e.g. bumper to bumper, manoeuvring, or stationary, they close (due to gravity pulling them down)
Then when the fan comes on, the partial vacuum created, pulls them closed even tighter. The advantage of
all of this is that at higher speeds, the air cools more of the radiator through the flaps and the fan aperture.
At slower speeds when the fan comes on, the flaps makes the shroud work efficiently by letting the fan pull air
through all of the radiator. Spal flaps are available from many outlets including Summit Racing.
Electric fan or original fixed propeller fan.
This has already been dealt with elsewhere on this site. Modern electric fans only come on when they are
needed. Most of the time they are off and there is no fan noise. Fixed propeller fans reduce horsepower,
increase fuel consumption and cool the car when it does not need cooling which in turn delays the heater
from heating the cab. Fixed fans run slow at slow speeds when the fan needs to be effective and fast at
high speeds when the fan does not need to be turning. New cars use electric fans for all of these valid
good reasons. As shown elsewhere on this site, I use a high performance "Spal" fan. Fan manufacturers
quote the maximum cfm (cubic feet per minute) which is the amount of air a fan can move through it. The
absolute cfm rating is not the complete story. As soon as a fan is bolted to a radiator or a shroud, the
cfm count goes down. In tests it has been shown that Spal fans when bolted up, have a lower decrease
in cfm flow rate than most other fans on the market. Also curved fan blades tend to be quieter
than straight fan blades.
Finally make sure your electrical system has been upgraded to deal with the high currents an electric
fan can draw, especially the transient switch-on currents. The 16" Spal
fan I use
is 3.5" thick.
Water pump clearance.
The existing clearance before the upgrade is about 7/8". The shroud will reduce this by 1/2".
It is very important to check how much space you have in front of the water pump so that the shroud
and fan will fit and still have some clearance space. Adding together the radiator at 2.5", the shroud
at 1/2" and the fan at 2.5" gives us 6.5". This leaves almost 1/2" (actually about 3.8") of clearance
to the water pump which is enough.
Note - Engineering Cooling Products sell a radiator, shroud and fan package but their fan is 4" thick
making a total of 7". This would not fit in the space forward of my water pump and besides I already
had a very good Spal fan which was 3.5" thick. Their complete package was $500. Unfortunately using my
own fan, new holes will need to be drilled in the shroud to take the Spal fan and existing holes for
their fan will need to be plugged. I am sure their fan is very good and it is always good to buy a
complete package but it will not fit my truck. It may fit yours.
Since the truck has an aluminium inlet manifold, a quality antifreeze is needed and it must be the type
which protects both steel and aluminium parts in the cooling system. Note antifreeze can damage
paintwork, especially if it is allowed to dry on it so wash it off if you spill any.
Automatic transmission cooling.
If you are running a V8 it is highly likely you will have an automatic transmission. The atf (automatic
transmission fluid) needs to be cooled and it is normal to run it through the special section at the
bottom of the radiator, however, it is also good policy to have, in addition, a extra transmission oil
cooler. So far this is all basic stuff but I would like to consider the following less well know issues -
1. Where is the best placement for a cooler on our "Advanced Design" trucks?
2. What kind of cooler is the most efficient?
3. Is a shroud and temperature cooled fan a good idea?
4. If you have an axillary transmission oil cooler, is it a good idea to route the atf through the
lower radiator section as well?
Before we start this discussion it is important to remember that the number one killer of automatic
transmissions is heat! This is therefore an important discussion.
The existing finned tube cooler is shown above. Below radiator and behind bumper.
Having the cooler in the air flow is always a good idea and therefore an ideal place to put it is
under the radiator behind the bumper. This location is not as good as in front of the radiator, but
in front of the radiator will reduce the effectiveness of the radiator and so below the radiator
(in my opinion) is the way to go. There will be plenty of ram air going under the car and through
the cooler in this location. This location restricts the height of the cooler to about 7 or 8 inches
and so it needs to be as wide as possible. The most common type of cooler is the finned tube variety,
and whilst this type is cheaper, it are not as efficient as the stacked plate cooler. Stacked
plate coolers can remove much more heat from the fluid. For all of the reasons above relating to
the engine radiator, shroud and electric fan, a stacked plate cooler with shroud and fan is going to
cool that valuable transmission much more effectively when there is no significant air flow at slow
speeds. In particular, when you are manoeuvring and changing gears. In my opinion, the fan which
seems to suite this purpose the best is made by Durale and is only 7.5" high (ideal) and 13" wide.
It uses a shroud and two 5" temperature controlled fans. There is a picture of this cooler above.
Radiator and transmission cooler pipe routing.
Now to the interesting discussion about whether, if you have an axillary transmission oil cooler,
it a good idea to route the oil through the radiator as well? Here are the arguments -
1. If you have an efficient stacked plate cooler with shroud and temperature controlled fan
it should not be necessary to prevent overheating.
2. It is possible for the bottom of the radiator to fail and water could get into your transmission
fluid which would kill your transmission. Whilst failures are rare they can happen.
3. There will be less pipes and connections if it is not routed through the radiator and therefore
less chance of high pressure fluid leaks.
4. Your radiator will be more efficient at cooling the engine if it does not have to cool the
transmission as well. (actually when you think about this one, it could work either way. If your atf
is cooler than the engine coolant, the routing through the bottom of radiator could be assisting the
engine cooling. Therefore since this issue could work both ways, whilst it is interesting, it is
not really a consideration.
5. Temperature stability and the theory that transmission can suffer from "cold fluid wear".
If you are routing through the radiator, the fluid will only have small temperature swings
and will not significantly swing away from the temperature of the radiator. By just using
a cooler, there will be larger temperature swings and it is possible the that lower fluid
temperatures may increase transmission wear. I can't say I am totally convinced of this
so I will keep an open mind. Heat kills transmissions but this is still worth considering.
Conclusion - Since I am using my existing radiator which I can trust, I will be routing
automatic transmission fluid through the bottom of the radiator as well as the cooler.
A deep, finned, aluminium sump pan can also assists in cooling the transmission.
Transmission oil (and filter) should be changed at regular recommended intervals.
There are many quality makes of atf, I use "B&M Original Trick Shift" which is one of the recommendations
from "Extreme Automatics" who supplied the transmission, however, it is no longer possible to buy this
atf in the UK and importing it is difficult.
Durale transmission coolers and Spal
fans are available from "Summit Racing
" and similar online stores.
The work on this cooling upgrade continues and this page will be updated later in 2018
May 2018. Radiator to engine (SBC) bottom hose with drain adapter.
One of the problems with the truck radiator is that there is no drain plug but this can be rectified with an inline
38mm to 38mm drain adapter. The second problem is that a Small Block Chevy V8 (Gen 1) has an inlet pipe of
45mm but the radiator bottom outlet is 38mm. A final issue is that this is a Hotrod adaptation. These trucks do
not come with an SBC engine and so no ready-made hoses are not available. This is how I solved these problems.
Silicone 90 degree hose reducer 45mm to 38mm from Ash on ebay but other companies sell them - £13.48
1.5 to 1.5 (38mm) drain adapter. JEGS Hose Drain Part Number: 555-51155 $23 + shipping.
Finding the best pipe with the correct wiggle to go from drain adapter to radiator took some time
but the Jeep Grand Cherokee WK 55116867AA radiator hose (from ebay) was ideal - £17.75
3 x 38mm and 1 x 45mm genuine Jubilee stainless steel clips from ebay (about £8.00)
These are high quality hoses and they were trimmed to size. Only the best stainless clips were used.
Breakdowns can happen due to hose failure and so this can be considered as preventative maintenance,
in addition, draining the cooling system is now an easy process.
May 2017 Hood ventillation tip.
When you lift the hood are you greeted with a face full of hot air? Cooling the engine with a fan is all very well
but that hot air needs to go somewhere. Cutting and removing some of the rubber sponge roll at the rear of
the hood lets hot air escape. It may be a small mod but it does help.