Lloyd Novak and Eric Forsberg


The following information may be helpful in selecting and using cooling system parts for conversion purposes. You should keep in mind that there are so many variables involved with the process of cooling an engine that its impossible to use hard and fast rules, but if you apply the following principles, you will be able to make the right decisions to add to the reliability and longevity of your Jeep vehicle. Overheating should not be a problem on a conversion if some basic rules are followed.

Many readers already know that Lloyd Novak has passed away. There was a great fear that his knowledge and willingness to help was lost. Fortunatley that has not happened.

Eric Forsberg now runs Novak Adapters and is following in Lloyd's footsteps by helping to get the knowledge necessary to perform a successful engine swap out to the Jeep comunity.

There is a tremendous knowledge bank in Lloyds notes, dating back to 1960, and this article is only the first in a series of articles that will benifit Jeepers everywhere.

It's nice to know that some things don't change.

John Nutter, JeepWire.Com Editorial Staff

Engine Condition and Tuning

An often overlooked area is the condition of the engine itself. Mechanically it must be sound and the water jackets of the block and head(s) must be free of contaminants that could act as an insulator, preventing proper heat transfer to the cooling media. A good flush of the cooling system and engine with the right detergents is a good way to eliminate this possibility. Engine compression, timing (both ignition and camshaft), as well as induction tract air leaks, thermostat (or the lack of one) are also among a few of the many cooling issues related to the engine itself that get overlooked too often.

The Radiator

Most people realize that radiator size is relative to good cooling. What may not be realized is that the core area in square inches is much more important than core thickness. As a general rule, it takes a minimum of fifty square inches more core area than displacement in cubic inches of the engine to be cooled.

As an example, a 283 c.i.d. Chevy V8 requires 283 square inches of core area plus at least fifty additional square inches of core, for a total of 335 sq. in. This could be an 18x19 core (342 sq. in.) or any other height by width combination to end up with the number of square inches needed. The actual size or configuration, be it cross flow or vertical flow, is not important as long as it will fit the area available and is large enough for the engine.

Many times a radiator will be found that has the proper core size but the mounting will be too wide or too tall, etc. The mounting flanges can often be trimmed or otherwise modified to work. Often, the radiator can also be turned around in its mountings to change the front to back location of the flanges. Sometimes a radiator may be found that is the proper size but one or both hose fittings may not be correct for the engine. These types of modifications can be done by a good radiator shop. However, be sure you dont end up with both hose fittings on the same side of the radiator or hot coolant will simply circulate and not pass through the core. This is an often overlooked item that can cause overheating on a conversion.


The relationship of the core to the fan is quite important also. The core should be parallel to, and no more than one inch away from the fan and should be centered on the fan. The core cannot be mounted to the back of the grill as there must be space for air to spread out so it can flow through the core. While on the subject of fans, we have yet to see an engine conversion that cools satisfactorily under all conditions with an electric fan. However, we continue to be hopeful as fans become stronger. For that matter, there may be some conditions of use that will result in above regular operational temperatures no matter what conditions prevail.

It is important to note that by the time air has passed through three sets of radiator tubes it has just about reached the temperature of the coolant and additional thickness does little to improve cooling. This varies with ambient temperature and speed of airfiow. It simply means that core area is much more important than core thickness. Another important factor related to airflow is mounting or carrying items on the front of the vehicle. Most Jeeps have a rather limited grille opening area. License plates, oil coolers, driving lights, toolboxes, winches, etc. will usually cause enough turbulence to disrupt airflow at some speed or other and this could result in overheating. Also, the mounting of an automatic transmission cooler in front of the radiator will measurably diminish engine cooling capacity as well. By the same token, a transmission cooler mounted behind the radiator will be subject to the heat flowing through the fins of the radiator, making it a poor location for transmission cooling purposes as well.

There may be situations that will result in less than ideal radiator to fan locations and these can be solved by shrouding the fan. This causes a vacuum which improves airflow particularly at low vehicle speed. Actually a fan shroud is a good idea under any condition.

There may be many suitable radiators and fan configurations for any swap. This info should help you choose one that may be available, rather than suggesting some particular one that may be hard for you to find.

Other Considerations

Cooling system operational temperatures vary also. Running hot in one systems application may be normal temperature to another. In other words, an open (or non-pressurized) cooling system will, of course, boil at 212 degrees Fahrenheit at sea level. This same system will be normal at 195-220 degrees F. with a 15-16 pressure cap and 50:50 mix of glycol coolant and water.

Another overlooked item is the accuracy of the temperature gage. Some gages may be considerably out of calibration. Either electrical or mechanical gages can be off by 20 to 30 degrees. One should always cross-check the temperature with a known good gauge. However, it has been our experience that the good mechanical gauge is more accurate and often preferable, though the routing of its pressure line is arguably more difficult than stringing a wire into the cab of the vehicle.

A coolant overflow recovery system should be used on pressurized cooling systems to make sure they stay full of coolant at all temperatures.


It is our hope that the cooling principles outlined in this article will assist you in putting together a quality cooling solution to your engine swap, or even just helpful for the maintenance and troubleshooting of a stock engines cooling system. The longevity, reliability and therefore, capabilities of your Jeep are dependant upon it.

Contacts: Related Links:
  • Novak Enterprises
    Dept ORN
    1 Novak Drive
    Novak Town Usa 11111
    Phone 1.877.602.1500

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