Many Pontiac owners just accept the fact that a high-horsepower engine is going to run hot on the street. Doug Tornello was one of them. His beautiful '67 GTO certainly fits the assumption. Sporting a 560hp, 510ci engine with an IA cast-iron block, aluminum cylinder heads, and 10.75:1 compression, all on 93-octane pump gas, this Poncho had the right to create an elevated coolant temperature if anything did.
The car had all the proper parts: a large Be Cool aluminum radiator and high-speed electric fan. However, around town and in traffic, the coolant would quickly go up to 240-plus degrees. Then the engine would run poorly, not only from the excessive heat but also the boiling of the fuel in the Demon carburetor. At a constant highway speed, the engine stayed cooler (200-210 degrees), but as soon as the GTO stopped moving, the gauge would spike up and stay there. This condition wasn't acceptable; Doug lived in worry of getting caught in a bad traffic jam, overheating and damaging the engine.
Diagnosing The Problem
The first step in reducing the coolant temperature of Doug's Pontiac is to diagnose the problem. The key element here is this Pontiac ran cooler at high speeds than around town and below 40 mph. A good rule in this scenario (assuming there isn't airflow restriction to the radiator) is to examine the water-pump flow rate.
Our subject Pontiac was equipped with an underdrive pulley system that featured a 6-inch-diameter water-pump pulley, which is larger than the stock Pontiac design. The larger pulley slowed the stock replacement water pump to the extent that at lower speeds there was insufficient coolant flow through the system, resulting in a higher coolant temperature. The first step was to locate a smaller (5-inch or less) water pump pulley.
When a search of the available parts was exhausted, Melvin Benzaquen of Classic Restoration Enterprises contacted Fred Bellscheidt of B&R Industries. This custom machine shop was able to create the desired smaller water-pump pulley to increase the coolant flow at low speeds. With the new pulley installed, the coolant temperature immediately dropped approximately 20 degrees around town and during slow driving, but the Pontiac still became ornery when it got too hot under the hood. There was a second component contributing to the problem.
Studying how an engine's cooling system works, you quickly see the traditional coolants, such as pure water or a mix of antifreeze and water, are much less than ideal. Though acceptable for a stock engine, one with elevated power needs more cooling efficiency than these liquids can handle. Evans Cooling Systems in Sharon, Connecticut, has developed a coolant called NPG+ (nonaqueaous propylene glycol) that doesn't use water, never freezes, and doesn't boil until 375 degrees. It's also a lifetime coolant, so maintenance is eliminated once it's installed. Before you can understand this completely new technology, a brief overview of coolant basics is in order.
(Editor's Note: The coolant basics portion of this article was excerpted by the author from his book, Engine Cooling Systems, from HP Books.)
The Attributes Of A Coolant
From the first use of water for cooling to today's modern engines, the basic elements that are essential for a liquid to function as an acceptable coolant have remained unchanged. In recent years, the list has grown even longer due to the different style of engines produced and the materials they use.
Let's first define the core characteristics of engine coolants and then expand into the requirements for a high-performance Pontiac engine.
As its name implies, the primary purpose of a liquid coolant is to remove heat from the cylinder head and engine block. Secondary concerns all apply to how the coolant transfers heat, its ability to be pumped, limit corrosion and deposits, offer lubricity and not freeze. As water freezes, it expands and would crack the castings of the engine if left unchecked.