Help is just a click away!
Click here to chat with a Speedway Team Member
Online - Chat with us!
Products to Compare (max of 3)
Compare These Parts
Talk to the Experts. Call 800.979.0122, 7am-10pm, everyday.
Customer Service
Since 1952
Talk to the Experts. Call 800.979.0122
Shop By
Street Race Truck More... The Toolbox

Fan Shrouds - A Critical Cooling System Component


You may think some of the things in your engine bay are pointless, like that fan shroud on the back of your radiator. We are here to tell you: LEAVE it there!

You may think that a shroud is a useless piece of plastic or metal, but they really do serve a purpose. They focus airflow through the entire radiator as compared to just the area that is covered by the traditional fan, creating a vacuum that pulls air across the entire surface area of the radiator, thus increasing cooling.

An un-shrouded fan is moving air through only the portion of the radiator equal to the surface area of the fan. See where we are going with this? If you spent the last week rebuilding your classic’s engine, would you really want to fry it because you didn’t think that shroud was needed? We thought not.

Let’s do a little math, shall we? (Don't worry, we did it for you!)

To calculate the area that is covered by your fan, use the formula below. As an example, we'll use a 17" diameter fan.

Area = (Pi) x (r2)

  • Area = (3.14) x (8.52)
  • Area = (3.14) x (72.25)
  • Area = 226.85”2

Now, for comparison, use the formula below to calculate the surface area of your radiator. We'll use a 27” tall universal radiator with a core height 22.25” and a core width 18.25” for this example.

  • Area = (Height) x (Width)
  • Area = (22.25) x (18.25)
  • Area = 406”2

Judging from the calculations above, you can see that without a shroud directing the airflow across the entire radiator, you are effectively not using 44% of your radiator. By simply adding the proper size shroud behind your radiator, you'll ensure that 100% of the radiator's surface area is used to cool your engine.

And here are a few more tips related to radiators and shrouds:
  • All shrouded fans should be on the engine side, no exceptions.
  • Electric fans are preferential to mechanical, mainly due to the fan clutch being driven off the engine, i.e., no mechanical power draw when the fan kicks on.
  • NEVER use the radiator as a ground. Electrolysis can result and it can destroy your radiator.
  • A commonly held thought is that fan blades should recess 50% into the shroud for optimum cooling. To get your fan in the correct position, use fan spacers or shims.

Products Featured in this Article

Related Articles

Radiator Cooling Performance
by Jason Lubken - Posted in Tech
Are you ready to replace that old radiator? Whether it's a factory or high performance application, we can help you choose the correct radiator with a matching fan shroud for your street rod.
Cooling System Principles
by Jason Lubken - Posted in Tech
Is your engine overheating? You've invested all that time and effort, but your gauge is still reading in the red. Let's take another look at the basics and make sure you're getting the best performance possible out of your cooling system.
Looking Beyond the Cooling System for Common Overheating Cures
by Jason Lubken - Posted in Tech
Have a monster radiator but your engine still overheats? We'll show you what to look for beyond the cooling system for common overheating issues.
Speedway Tech Talk - Electric Cooling Fans
by Pat Orth - Posted in Videos
Pat gives some tips about choosing the right fan for your application.
Wiring Dual Electric Fans
by Matthew McClure - Posted in Tech
The benefits of using dual electric fans vs a single fan, and the steps on wiring them into your car.
Protect Your Radiator With Nomex Honeycomb
by Jason Lubken - Posted in Tech
Tired of straightening damaged fins or replacing your new race radiator? Try protecting it with a sheet of Nomex honeycomb and let it take the beating instead of your expensive radiator.
Speedway Tech Talk - Keeping it Classy with Motor Meters
by Pat Orth - Posted in Tech
Speedway Motors employee Pat joins us once again. This time Pat is talking to the Model A and Model T owners, specifically in regards to Moto-Meters and accessories.
32 Radiator Install
by Tim Matthews - Posted in Tech
Speedway Motors employee Tim M. keeps his cool with a custom install of a 1932 radiator in his 29 roadster project. Follow along as he walks step by step through the process.
Electric Fans
by Speedway Tech Team - Posted in Tech
Answering a few common questions regarding electric fans.
Single Pass, Double Pass, Triple Pass radiators; what’s the difference?
by Jason Lubken - Posted in Tech
Ever wonder what the difference is between single, double, and triple pass radiators was? Click here to find out!