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

Looking Beyond the Cooling System for Common Overheating Cures

9/14/2016
Overheating

The hardest part about keeping your gauges out of the red on a street rod usually happens after you start changing what the factory did. But wait, isn’t the core of street rodding all about changing the factory design? After V-8 engines get dropped in place of four and six cylinders, space becomes a premium and you're left with figuring out how squeeze the biggest radiator you can fit into a crammed engine compartment. The struggle comes in when there’s no longer a standard guide to use — you become the engineer so to speak. But with the technology involved in today’s performance parts, there shouldn’t be any reason we can’t keep our rods running cool. There may not be a set-in-stone guide on how to keep every street rod cool, but there are some known good rules to go by when it comes to the cooling system.

One of the first things you can examine is: at what point is your engine overheating? Does it happen all of the time or just when you’re in traffic? The radiator must have air moving across it to carry away the heat, so if you’re on the highway and it stays cool, but at a traffic light it starts to overheat, the issue is usually related to airflow. The next questions you can ask are: do you have the proper cooling fan in place? And are you using a fan shroud? Consider the path of least resistance — the same is true with airflow. If you have a shroud in place to channel incoming air, it’s forced to travel through the radiator.

So what happens when you have already replaced the radiator, the water pump, and added a new cooling fan, but the car is still running hot? If we look at the source, a stock engine produces about 42 BTU per horsepower and after performance upgrades even more. When a vehicle is overheating and you have new components in the cooling system, it’s time to start pointing your finger somewhere else. The engine may be creating too much heat due to factors other than the cooling system.

Air/Fuel Mixtures

A proper air/fuel mixture will help your engine run cool and to its full potential. Most overheating issues related to air/fuel ratios are the result of a lean mixture, which causes the cylinders to run hotter. On most carbureted systems, fuel pressure typically ranges between 5 and 8psi at all speeds. It’s important to maintain that pressure under all load conditions, because if it drops off at higher rpms, you run the risk of going lean. As a general rule of thumb, most stock engines use roughly 14.1:1 to 13.4:1 air/fuel ratio at idle and slightly richer at high rpm. So having a quality fuel pump and a correctly tuned and jetted carburetor is a must for proper fuel efficiency.

There are a few ways you can check your air/fuel mixture. Many automotive shops use an exhaust gas analyzer, but not everyone has access to tools such as this. As an alternative there are several aftermarket manufacturers who supply air/fuel monitors and wideband tuners that provide readouts from the exhaust. Or another way to gauge your fuel mixture is by examining your spark plugs for abnormal burn characteristics.

Ignition Timing

Considering the principles of ignition timing, if the spark occurs to soon or too late, the cylinders will run too hot and the engine can suffer from power loss. If the spark happens too soon, the engine fights against cylinder pressure which may cause a pinging problem. When the spark occurs too late it won’t completely burn compression gasses which creates more heat that the cooling system has to dissipate. The optimum ignition spark timing will vary with engine speed, load, and air/fuel mixtures. And the correct ignition timing involves more than just setting the initial timing; the amount and rate of the mechanical and vacuum advance curves are also very important to avoid overheating. This is because cylinder pressure is much higher at wide open throttle than at midrange. The lower the cylinder pressure is, the more time it takes to complete the combustion process.

Checking the Thermostat

You should always use the correct thermostat for your engine. Without a thermostat the engine would have no way of regulating the minimum heat range. The bottom line is that the manufacturer designed our engines to run with them installed. Every engine has an optimal heat range to run efficiently, in general 190°F to 210°F. On most carbureted engines, a common thermostat used is a 180°F.

You can check the function of your thermostat a number of ways. One method is by letting the engine come up to operating temperature while feeling the upper radiator hose, once the thermostat starts to open, you should feel the hose start to take pressure and get hot. You can also use an infrared heat gun on the thermostat housing to observe the temperature change as the engine warms up. Some may even remove the thermostat and check its function in a pot of hot water with a cooking thermometer.

Water Pump and Pulleys

If a water pump is leaking it almost always means the pump has failed and needs replaced. Before you install a new pump, always check to make sure the impeller spins freely and has minimal end play. If it’s a high performance engine, high flow water pumps have been proven to help with coolant flow. You should always use the correct size pulleys according to what was on the engine from the factory. It’s not recommended to install under-drive pulley kits on street driven vehicles. Undriving the cooling system (spinning the water pump slower) can lead to poor cooling performance. If you're buying an aftermarket water pump be sure to pay attention to the direction of rotation. Some of the later style aluminum water pumps with a serpentine-belt drive system used a reverse rotation pump, which can lead to serious headaches if overlooked.

Products Featured in this Article

Related Articles

'57 Bel Air Fuel Pump
by Jeff Karls - Posted in Tech
2/12/2018
The process of changing out a mechanical fuel pump in a 1957 Bel Air and some helpful tips while doing so.
How To Choose A Radiator For Your Car
by Jason Lubken - Posted in Tech
9/14/2016
Learn how to choose the best radiator for your vehicle. Our guide covers key factors to consider when selecting an aftermarket radiator for your street rod.
Reusable Car Air Filters vs Disposable
by Speedway Tech Team - Posted in Tech
9/13/2016
Learn the cost differences between a reusable and disposable air filter for your car with our guide. Learn how to clean a reusable car air filter as well.
Wiring Dual Electric Fans
by Matthew McClure - Posted in Tech
2/27/2018
Learn how to wire dual electric radiator fans. Use our dual fan wiring diagram and guide to make sure you properly wire your fans to your thermostat.
Winterizing Your Fuel System
by Frank Galusha - Posted in Tech
1/30/2018
The process on how to effectively winterize your fuel system in open wheel racing. This includes step by step instructions and recommended parts to use for your fuel system.
Cooling System Principles
by Jason Lubken - Posted in Tech
9/19/2016
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.
Fuel System Overview
by Speedway Tech Team - Posted in Tech
9/13/2016
Thinking about rebuilding your fuel system but you're not sure what it entails? Click here for a comprehensive article on what to expect!
Red Ram Revival Part Two
by Tim Matthews - Posted in Tech
7/12/2016
Speedway Motors employee Tim M. Decided to take us along as he revives his 241 "Baby Hemi". In this installment, Tim helps his project breathe a bit better with and Edmunds 2x2 intake, topped with a pair of Speedway Motors' own "9 Super 7" carbs.
Speedway Tech Talk - Electric Cooling Fans
by Pat Orth - Posted in Videos
12/8/2016
Pat gives some tips about choosing the right fan for your application.
Approved Upgrades for the GM Crate 602/604
by Speedway Tech Team - Posted in Tech
7/7/2016
Tips and tricks to pull the most from your GM 602/604 platform.
Suggestions
`
Error
X
Note
X
Ok