Keep Your Cool
You may not think about cooling systems when you think performance, but you should. Our Tech Insider has some tips.
Words: Larry Shepard
If you are a typical automotive performance enthusiast, the cooling system is probably not the first thing that comes to mind relative to your engine or car. Typically the cooling system is one of the last things that you might consider. You may have built or assembled your high-performance engine and selected every part for the engine—but the cooling system probably wasn’t included. Most of us don’t concern ourselves with the engine’s cooling system unless we have a problem. Everyone will approach their cooling system with somewhat different goals, so I’ll discuss it in general. Simply put, there is more to a cooling system than you might believe.
In a technical sense the engine makes heat and the radiator dissipates heat. The balance between these two functions determines whether your engine overheats or stays cool. In the old drag racing days, the racers did everything they could to hurt the cooling system, like installing a small radiator for weight savings. Good for weight and weight distribution, but not good for maintaining engine temperatures. But it’s important to remember that drag racing was only 1,320 feet. Today you have many more considerations such as restoration and cruising, where the speeds are low and underhood temperatures tend to be high. There is lots of science inside the engine that relates to the cooling system, such as the water jacket in the head and the water jacket in the block. As a general rule, the more water that the cylinder head holds the better, but no one publishes the size of their water jacket. Therefore stock based heads and cast iron heads tend to be better choices while big-port heads tend to require smaller water jackets and therefore may not be your first street choice. This tends to be a tough call based on available information. The siamesed-bore cast iron and aluminum blocks like the 440 and 426 HEMI® versions from KBRE (Keith Black Racing Engines, www.keithblack.com) like to have steam-holes drilled at the tops of the water-jackets, and matched in the head gasket and head itself to help avoid hot spots.
The block and heads make the heat, and the heat is transferred to the water which is pumped by the water pump. There are many styles of water pumps. On the B-RB-426 HEMI engines, start with the aluminum housing P4286900 that holds the water pump to the block and add the aluminum water pump P5007643AB (most production pieces are cast iron). The A-engine pumps are aluminum and have a 6-blade (P5249558) and an 8-blade (P5249559) version. The A-engine pump mounts to the aluminum front cover like P5249930. The B-RB-HEMI front cover is P4349816 (chrome). The typical water pump is driven off the crank by a fan belt, typically a V-belt. Production replacements for these fan belts are available from Quanta Products (www.quantaproducts.com). There are serpentine belt conversions that are available from March Performance Pulleys (www.marchperf.com). With a serpentine belt-drive system, similar to that used on the Magnum V8s, one multi-groove belt drives all the accessories on the front of the engine, instead of having a fan belt, a power steering belt etc.
The typical production engine uses an overdrive pulley ratio, which means that the water pump runs faster than the engine. This is good for low-speed cooling but not good for horsepower at high speeds. Generally the amount of overdrive is about 20 percent. The production steel pulleys for the 426 HEMI are P4510282 (water pump) and P4510286 (without power steering). There are black and chrome steel pulleys for the A-engine and B/RB engines available from Year One (www.yearone.com) and Mancini Racing (www.manciniracing.com). If you underdrive the fan/water pump (and alternator), you will make more power. Underdrive pulleys are available (billet aluminum) from March Performance Pulleys. Generally the street versions of these March pulleys underdrive the water pump about 20 percent or 80 percent of the crank speed. Tip: if you try these HP pulleys, you may need a shorter fan belt(s) than standard.
On the racing end of the water pump spectrum are the billet electric pumps from Meziere (www.meziere.com) and CSI (www.csiperformance.com). There are also systems that drive the water pump with an electric motor and a small cog-belt rather than from the crank. These are available from Moroso (www.moroso.com) and Mancini Racing. These racing systems aren’t really designed for the street. The standard production engine used a fixed, 4-blade fan 03462185. The viscous fan unit P4120758 is a basic 15 hp gain over almost anything.
The water flow from the water pump to the radiator is controlled by the thermostat. For models up to 1978 there is a 180° thermostat P4876307, along with a 195° version P4876308 for the 1979 and newer units, which is smaller than the older unit. They are not interchangeable. Milodon (www.milodon.com) offers 160° and 180° thermostats. The thermostat sits in a short, straight housing—chrome P4286759 for up to 1978 and chrome P4452025 for 1979 to ’92. Tip: high-performance and aftermarket (on the A-engine mainly) parts, like intake manifolds, may not reflect the stock size or center location of the older (pre-1978) units. There is also a 90° aluminum water neck (thermostat housing) P5249191, which takes the bend out of the top hose and also has three positions so you can point the outlet at the radiator inlet. The B-RB-HEMI thermostat sits in the top of the aluminum housing mentioned earlier. The A-engine thermostat sits in the front of the engine’s intake manifold. Therefore the A-engine uses a by-pass hose to get from the manifold to the water pump; use HD silicone hose P4876373.
To get the water from the engine/water pump to the radiator, you need the upper and lower radiator hoses. These hoses are available from Year One and Goodyear. Production radiators are available from Glen-Ray Radiators (800-537-3775). A high-performance radiator (aluminum) is available from Be Cool Radiators (www.becool.com). The Be Cool high-performance radiator can be made to the car’s radiator yoke opening, which can provide a little more capacity than the standard big radiator (typically used on the 426 HEMI and 440 cars). For the production radiators, there is a production-style 16# radiator cap (77R06021). Overflow bottles are available from Mancini Racing. While not necessarily required on a drag racing package, all street applications should use a radiator fan shroud (P2785434) for the 1967-1969 B-Body big block or P2998326 for the 1970-1973 B- and E-Body big blocks. These units may be adapted to other models. The shroud fits over the outside edge of the fan and around the outside of the radiator, which helps makes the radiator more efficient—very important at low speeds. Production cars have two basic styles of radiators: manual and automatic transmission. The automatic transmission radiator has a bottom tank with fittings at the bottom of the radiator, one on each side. The manual unit does not have a bottom tank for transmission cooling. Obviously you can use the automatic transmission version with a manual trans but the reverse is not true. This setup is OK for the small blocks and the 145K-style converters but if higher stall converters are planned, you should add an additional, separate auxiliary cooler, like P4876916, in front of the radiator.
Tip: while this wasn’t much of a concern in the 1960s and ’70s, today detonation is a major concern. Detonation will make the engine run hot and the cooling system is often blamed. However, detonation is most frequently caused by too much compression ratio balanced against the octane level of the gas being used. The cooling system cannot solve these detonation problems. This is easy to say but it is very difficult to troubleshoot because many of the characteristics are the same. My recommendation today would be to assume the detonation/compression ratio cause first.
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