Harleys and Super Villains

Over the summer, my Harley Street 750 has been my primary mode of transportation around the urban jungle of Chicago. If you’re not up on Harleys, the Street series bikes are a bit of a deviation from the standard Harley formula. For starters, it’s liquid cooled and aside from the Porsche designed v-rod, all Harley’s are air cooled engines. It’s also lightweight (by Harley standards), coming in at 460 lbs compared to Sportster Iron 883 which is 550+ lbs.

Which makes it easy to navigate the 27 stop lights on my 6 mile journey into our shop everyday. Without traffic, that’s 30 minutes. If you’re doing that math, that comes out to 12 MPH without unusual traffic. As they saying goes, that’s life in the city.

Another deviation from the Harley norm is the camshaft design. All Harleys, aside from the v-rod, are push rod engines as opposed to overhead cam designs. This will probably never change as the pushrod design is what give Harley’s that unique rumble sound. However like it’s v-rod cousin, the Street series bikes are over head cam engines. Essentially, the Street bikes are smaller cousins of the v-rod.


This is my Street as I bought it on Craigslist. You’ll notice something about it – it’s black. Very black. Our shop manager Enrique said if I had a cape while riding it, I would look like a super villain. Which leads me in to todays topic – painting your radiator black.

We receive lots of questions from customers about painting their radiators. Some guys just don’t like the buffed look of our radiators and prefer something low key or stealth. There is a lot of misinformation out there on the interwebs so I thought I’d dispel the myths about it. There are three main ways to turn your radiator black: painting, powder coating and anodizing.

It is OK to paint your radiator – as long as you use the proper type of paint. Conventional spray paint like Krylon or Rustoleum will not work for painting your radiator. These types of paints are going to inhibit the heat transfer and you’ll likely ruin your radiator by doing it. For a simple black look, the best option is to use the water based paint that Eastwood sells. It’s under $20 and the most economical approach to turn your radiator black.


One of our Tri-5 radiators powder coated black

However something that a lot of guys aren’t aware of is that you can powder coat your radiator with no downsides. In fact, this is the best method for turning your radiator black. Because of the nature of the powder coating process, it does not inhibit the heat transfer of the radiator. In fact, many OEM radiator manufacturers powder coat their radiator cores for the superior corrosion protection it offers.

Lastly there is anodizing. This also works well however it requires that we us a special filler rod in our welding process, otherwise the radiator will severely discolor in anodizing. We don’t really recommend anodizing since it’s expensive and doesn’t really look as nice as powder coating. And unless you’re 100% sure your radiator was welded with a anodizing friendly filler rod, you’re going to end up with a discolored mess. And a lighter wallet.

For a while, we offered some of our more popular models with a black powder coat option. We still have a few left for the 55-57 Chevy, 66 – 67 Chevelle and 68 – 74 Chevelle. These are not something we’re likely to offer again since these were really not that popular. When they are gone, they are gone for good.

If you’re looking for a simple black option for your radiator, give Frank in sales a call (773)303-6291 or frank@speedcooling.com and he can set you up with one.

Three Row Snake Oil: The Gift The Keeps On Giving – Giving You Grief.

Let’s review what we’ve learned in the previous posts. We learned that there are many old wives tales about aluminum radiators, most of which are not true. Then we learned that aluminum is lighter and stronger than copper/brass. As hot rodders, we exploit this lighter and stronger aspect of aluminum to build aluminum radiators that cool significantly better than their copper/brass counterparts.

The reason aluminum cools better is quite simple: bigger tubes. Bigger tubes are a culmination of all the positive aspects of aluminum put into action. Bigger tubes means fewer, larger tubes are needed to get the same amount of cooling done. Because there are fewer tubes, there are fewer tube gaps. These tube gaps act like speed bumps and slow down the cooling air as it flows over the core.

Back in the era of copper/brass radiators, snake oil companies started building cheap 4-rows. They did this by using tall fin heights and small tubes. A cheap 4-row radiator would have 32 rows of tubes vertically and only use ⅜” tubes. A good high quality 4-row will typically have 38-40 rows of ⅝” tubes. That’s a huge difference.

Just like the snake oil 4-row copper/brass radiators, there are snake oil aluminum radiators. These come in the flavor of 3-row and 4-row aluminum radiators with ½” cooling small tubes. From our previous discussion on aluminum, you might be wondering why would anyone want to make aluminum radiators with small ½” cooling tubes? Doesn’t that defeat the entire benefit of using aluminum with larger, fewer rows?


Yes, it does defeat the entire purpose of aluminum. So why would anyone make an aluminum 3-row or 4-row radiator? The reason is quite simple: to lighten your wallet and fatten theirs. They are suspecting you aren’t educated on radiators enough to know the difference. And in most cases, they are correct. It’s a marketing gimmick.

These 3-row and 4-row aluminum radiators are made in China. And the reason is quite simple, because no reputable American company would ever build an aluminum radiator with less than 1” cooling tubes. In fact, you are far better off with a 3-row copper/brass radiator than you are with a 3-row aluminum radiator.


Enter the Chinese invasion. If you know anything about the Chinese, they will literally do almost anything for money. Even if it makes zero engineering sense. No reputable cooling company will ever sell you a 3-row or 4-row aluminum radiator with less than 1” cooling tubes. Yet the Chinese are more than happy to do it since they have zero to no morals. They will do anything for the precious American dollar.

You will see these 3-row and 4-row gimmick radiators all over the internet. And they make outrageous claims of being able to cool upwards to 700 horsepower, which isn’t true at all. So you may wondering, if this isn’t true, then how can they be selling these things without customers complaining all over the place that they don’t cool well?

That is the second piece to the snake oil puzzle. Most of the people buying these 3-row and 4-row gimmick radiators have low horsepower engines. The guys buying these radiators that truly have high horsepower engines are finding out the hardway: 3-row and 4-row gimmicks are not going to cool a high horsepower engine in the summer heat.

We know this since they are blowing up our phone as soon as the weather gets hot. They are baffled. They bought this radiator off Ebay that said it would cool 700 horsepower, yet it won’t cool their 375 horsepower engine with air conditioning in the summer heat. What is wrong? Well, what is wrong is that they were sold a gimmick with unrealistic claims.

The timing of this revelation is usually uncanny. The reason you build an engine and use good components in your hot rod is so it’s reliable. It really sucks it’s 90 degrees outside and you click on your Vintage Air setup only to find your engine overheats. And it really, really sucks if mama is in the car. You just spent a small fortune upgrading your cooling system and your engine is still overheating.

Yes, this does suck. However you are now enlightened and able to steer clear of the 3-row gimmick.

In our next e-mail, we will discuss the Super Gimmick Combo guaranteed to cause you grief: 3-Row Gimmick Radiator with Gimmick Fans.

Falling For The Three Row Gimmick

In our last post, we covered copper brass radiators and compared them with aluminum. We left off by comparing the thermal conductivity of aluminum with copper/brass. Copper/brass has almost twice the thermal conductivity of aluminum. Yet, aluminum radiators can transfer a lot more heat than their copper/brass counterparts and keep your engine running a lot cooler.

So how in the world can this be?

Aluminum is a much stronger material than copper, which is what gives aluminum a huge edge in keeping your engine running cooler. Why the strength matters comes down to the radiator tube size. Aluminum radiators are typically made with 1”, 1-¼”, 1-½” and 2” cooling tubes. Copper/brass radiators are typically made with ⅜”, ½” or ⅝” cooling tubes.


As you can see, aluminum radiators are made with much larger cooling tubes. These larger cooling tubes are the reason why aluminum cools better. And the reason aluminum radiators use larger tubes is because aluminum is stronger. If we tried to make a copper/brass radiator with 1” tubes, the tubes would burst because they can’t handle the pressure. That’s why the largest cooling tubes use in copper/brass radiators are ⅝”. With aluminum radiators, cooling tubes can be made up to 2” in size. That’s a 3.5 fold difference.

Why does size matter?

Like in many areas of life, size does matter. Let’s compare two radiators. The first is a copper/brass radiator with 3-rows of ⅝” tubes. Doing some simple math, the total cooling surface area is 3 x ⅝” or 1-⅞” total of cooling surface area. To put it in decimal, 1.88” of surface area.

The second radiator in our comparison is a 2-row aluminum radiator with 1” tubes. Doing some math again, and thankfully if math isn’t your thing, this math is simple: 2 x 1” = 2.0” of cooler surface area.

So the aluminum radiator has a slight edge over the copper/brass radiator in terms of surface area. Yet the copper/brass has a huge lead over the aluminum in thermal conductivity. Which might lead you to believe there is something else at play that gives aluminum an advantage over copper/brass. And you are correct.

The main reason aluminum performs so much better than copper/brass is tube gaps. Tube gaps are the spaces between the tubes in the radiator core. Because copper is weaker than aluminum, copper requires larger tube gaps in the radiator. This is because if the wall thickness in the header is too thin, the header will crack. On copper/brass radiators, the tube gaps are typically ⅜”. Yet on aluminum radiators, the tube gap is only ¼”.


These tube gaps are hugely restrictive to airflow across the radiator core. They are like giant speed bumps that slow the air down and cause higher pressure drops across the radiator core as air flows across it. How does this affect your cooling?

Well, it’s quite simple. Let’s say you have a 2500 CFM 16” electric cooling fans. When cooling fans are rated for CFM, they are rated with what’s called a no-load condition. That means if you held the fan up in the air with no restriction in front of it, it would move 2500 CFM. Yet when you bolt it on to a radiator, it’s going to move a lot less air because it now has to pull air through the radiator core.

This 2500 CFM fan bolted to the 3-row copper/brass core might only move 1100 CFM of cooling air. Yet the same cooling fan bolted to our 2-row aluminum radiator might flow 1700 CFM, even though the core is thicker than the copper/brass radiator. How can that be?

It’s because of the tube gaps. Tube gaps make a HUGE difference in airflow of a radiator core. The fewer and smaller the tube gaps, the better the core will flow. You can see the aluminum has only 1 tube gap whereas the copper/brass radiator has 2 tube gaps. This difference in tube gaps is what gives aluminum a HUGE advantage in keeping your engine cool.

There are also a few other reasons that give aluminum a significant advantage over copper/brass radiators.. Since aluminum is a stronger and lighter material, this affects how dense the cooling fins can be. If the core becomes too heavy because of the weight, the fins at the bottom of the radiator can collapse because they can’t handle the weight of the radiator.

This is where aluminum has a triple advantage. Not only is it stronger, it’s also lighter. Which means the fins can be made with thinner material while still keeping the structurally core radiator strong. Thinner material results in much more efficient heat transfer. And since the material is much lighter, that means we can crank up the number of fins in the core without causing the fins at the bottom to collapse from the weight above it.

By the way, I don’t recommend handling electric fans that are not mounted to a shroud. You may think electric fans are not powerful enough to do harm, yet they are extremely powerful and need to be handled with care. I speak from experience since I lost ½” of one of my fingertips testing fans! Electric fans can be extremely powerful and need to be handled with care.

So in the next e-mail, we will tie it all together and how you how just like snake oil companies came in and sold snake oil 4-row copper/brass radiators, they have now moved into selling snake oil 3-row aluminum radiators.

Copper Brass Radiators Versus Aluminum Radiators

Back in the day, if you needed a new radiator for your hot rod, your buddy probably said:

“Just get yourself a good 4-row”

Before aluminum radiators were around, the only upgrade from a factory 3-row radiator was either a 3-row high efficiency model or a 4-row. A 4-row added another row of cooling tubes which provided approximately an extra 20% of cooling power over a 3-row. Back 30 years ago, you could roll down to your corner radiator shop and even have him ‘recore’ your factory radiator with an upgraded 4-row core.


However like many thing in life, not all 4-row radiators are made the same. Back in the day, there were snake oil radiator companies that made cheap 4-rows. One way they accomplished this was by using tall fin heights and smaller tubes. A good 4-row radiator would have 4-rows of ⅝” tubes where as a cheap model would have 4-rows of ⅜” tubes.

These snake oil companies took advantage of most people’s ignorance and sold them a cheap 4-row that wasn’t likely to cool any better than the 3-row they had. Infact, in many cases, it might even cool worse.

Fast forward from the 1970s to the 1980s. Fuel economy is now becoming important and car manufacturers are looking for ways to make lighter cars. Switch the radiator from a copper/brass to aluminum model can save 10-20 lbs in many cars. For us hot rodders, weight is bad. So ditching the copper brass radiator for an aluminum model is a no brainer.

There are many old wives tales about why aluminum radiators cool better. The most common one is ‘aluminum dissipates heat faster than copper’, which isn’t true at all. Copper is an excellent thermal conductor. In fact, copper has almost twice the thermal conductivity of aluminum.

Yet, despite having a much lower thermal conductivity, aluminum radiators can transfer a lot more heat away than their copper/brass counterparts. You many be wondering how in the world that can be? It’s a great question with a simple answer, which we will explain in our next e-mail. Watch your inbox for the next few days.