Power Talk

Race
Engine
Cooling

Problems
and Solutions

What does it take to keep a high-strung racing engine cool at punishing RPMs and WOT operation? You can be sure the winners know, because wheel-to-wheel racing leaves little time to worry about your temperature gauge or the pre-ignition rattle in your expensive engine. Once the green flag drops, the cooling system must function properly for the duration, or you DNF (bad) or your engine's toast (really bad).

Kevin Enders, owner of Enders Racing Engines, Syracuse New York has been a machinist for 22 years, and building racing engines for about 15. He primarily builds big-block Chevy and small-block Fords for a variety of racing series, including dirt modifieds, USAC Silver Crown contenders and Super modifieds. Some of his customers include Billy Decker, Brett Hearn, and Pat Abold. Following are his comments regarding engine temperature control.

I've seen my share of performance engine cooling problems over the years. As an engine builder, it's important to me that the engines going out of my shop door keep their cool. After all, my pride and reputation are riding on their performance. Like all engine builders, I have a stake in the reliability and longevity of his products.

I've heard the comments racers make from time to time about an engine that "runs hot" and the finger of blame is usually pointed at the engine. My opinion is, if it's running hot due to a tuning problem or incorrect assembly, it'll blow or seize before long. But if the engine's put together right and tuned correctly, with proper clearances, it should tend to run cool. If an engine keeps running but it's consistently hot or there's a recurring detonation problem, then it's likely a symptom of a cooling system deficiency.

THE MOST COMMON PROBLEMS
One is the racer that just uses a radiator and pressure cap, similar to a stock configuration. There's air and vapor present in every cooling system, and it can cause problems if it's not removed. Trapped air may cause an air "lock" in a freshly filled system, preventing the flow of coolant. Air and vapor in a cooling system can also result in cavitation, the formation of an air pocket downstream from an obstruction or object moving in it, such as coolant pump impeller blades. This problem causes an already-marginal factory pump to lose considerable pumping efficiency in high RPM operation.

A Solution is the installation of a separate expansion tank, mounted as the high point of the cooling system. We're not talking about an overflow or catch tank, but a pressurized remote expansion tank that allows any air and vapor in the cooling system to rise to it. That gets the air and vapor out of the normal coolant circulation.

Another problem is some racers' dedication to one brand of radiator. I've seen noticeable differences in radiator brands over the years. Occasionally a problem occurs when a racer buys a radiator based on outside dimensions, from the supplier that sold them their last one. If the tube / fin spec's have changed since the last purchase, those details don't always get noticed. The new cooler gets bolted in, the running temperature goes up, and the racer thinks "Well... it can't be the radiator - it's brand new!"

And performance engine overheating isn't limited to dramatic boil-overs spewing huge clouds of steam. Some of the most serious overheating occurs deep in the engine's cooling jackets, in the form of localized overheating and hot spots. What makes this form of overheating so serious is that it sometimes occurs without being recognized until disastrous engine damage develops. These hot spots cause detonation, and ultimately, the destruction of the engine.

As you already know, detonation can occur due to common causes such as fuel (incorrect octane or mixture), cam or ignition timing, or incorrect plug heat range, among other things. But my customers don't usually suffer from these common maladies - they're way too experienced.

Instead, when a performance engine is pushed hard, the high heat generated by the combustion process overwhelms the ability of a stock, or stock-like, cooling system to absorb and carry off the increased heat. Ethylene glycol and water (EGW) coolants, even in a pressurized system, boil around 250º F. The combustion heat rapidly overcomes EGW coolant's ability to absorb it, carry it off, then shed it efficiently in the radiator. This may go unnoticed during a race, when the driver has so many other sensory inputs demanding his attention.

When detonation (or the damaged it's caused) is discovered, the coolant isn't always fingered as the culprit. Racers start looking for other ways to move their old style coolant, or sometimes slow its movement, though the cooling system. Thermostats get replaced with flow restrictors, higher capacity coolant pumps get installed, or a fan may be replaced by one with more blades, or one that's electrically-driven.

The performance aftermarket offers any number of fixes for hot-running engines, but before you go adding anything, make sure the basics are covered:

• If you changed something just before a noticeable temperature increase, un-change it, or find out why its performance (or lack thereof) was different from the previous part.
• There's gotta' be airflow. If your favorite flavor of racing involves dirt, make sure the radiator fins are clean and straight, and any baffles, screens, or deflectors are mounted where necessary.
• Be sure your cooling system is completely filled - give the coolant time to circulate, and allow as much air as possible to escape before you button it up. If you've filled your system but haven't eliminated all of the trapped air, you're going to encounter cavitation, hot spots and possible detonation problems. Consider installing a small air bleed fitting in the top of your coolant pump or other high point in your cooling system. It's notable that some new cars now come standard from the factory with cooling system air bleed fittings installed for this very reason.
• Resist the temptation to increase coolant flow rates by spinning the pump faster with a smaller-diameter pulley. Not only does that aggravate cavitation at the pump impeller, but it may lead to belt and bearing failures. There are high-flow coolant pumps available from the likes of Evans, Edelbrock, Weiand and others, and high-flow thermostats too. Improve your coolant flow with greater volume, not faster pump speeds.
• Keep an eye on your hose connections, especially if you're using silicone hoses. Silicone doesn't bond to connector tubes like conventional hose materials, so clamp tension and integrity are important.

Although I don't dictate which coolant my customers ultimately use in their engines, I recommend the installation of Evans Cooling Systems' NPG Coolant. 'NPG" stands for Non-aqueous Propylene Glycol, a patented coolant mixture that does not contain water. Among its many desirable properties, Evans NPG Coolant features a boiling point of 369° F in a no-or low-pressure cooling system.

That's important because, when water-based coolants encounter the extreme heat a performance engine generates in cooling jackets, they begin to boil so rapidly that a vapor barrier actually forms between the jacket wall and the coolant. This vapor barrier ultimately acts as an insulator, preventing the transfer of more heat from the jacket wall to the liquid. This phenomenon actually aggravates the localized overheating problem, causing hot spots to form, and resulting in destructive detonation.

I don't mean for this to sound like an ad for one brand, but this stuff works. NPG's unique composition allows it to keep removing heat from even the hottest-running engines. Its unusually high boiling point prevents the formation of a vapor layer, so the heat transfer from the cooling jacket wall to the coolant is constantly maintained. This quality gives my customers "insurance" against destructive localized overheating and detonation. I've found that, as long as there's sufficient coolant in the system, localized overheating and detonation are virtually eliminated with the use of Evans NPG. The added safety of using a no- or low-pressurized cooling system greatly reduces the chance of any scalding accidents, and it serves to extend cooling system component life too.

So far, my primary interest in recommending Evans NPG Coolant to my customers has been the safety margin it provides against overheating and detonation. Although the Evans web site (evanscooling.com) goes into considerable detail about the power gains achievable with Evans NPG-cooled engines and the right modifications, I haven't ventured into that arena yet.

But with the new year, and a new racing season upon us, I admit that I'm considering some experimentation. I've been curious about taking advantage of the increased compression and tuning benefits Evans says their NPG coolant allows. I feel that I owe it to my customers to investigate the potential performance increases, as long as engine reliability doesn't suffer.

I intend to keep on building reliable, winning engines that will keep my customers, and my shop's good name, in the fore front of the sport well into the 21st century.

-by Kevin Enders
Enders Racing Engines