Flathead Fever
Well-known member
This has been a great discussion. I’m now convinced that the restrictors will do more harm than good.
I keep a data base in my computer of flathead articles that have appeared in different hot rod publications from the past sixty-plus years. I remembered reading a story about installing restrictors and I was able to go into my data base and locate the article. In the October 1952 issue of Hot Rod Magazine there was a huge article on “How To Keep Your Engine Cool”, one section of the article was devoted to “Cooling Tips for Racing Engines”. I believe this article is the source of the restrictor myth. As this racing tip was past down from generation to generation of flathead enthusiasts somewhere along the way the part about it only being a modification for racing engines was omitted. Here is the racing part of the article, there is a lot of good info in it.
Jerry
“Cooling Tips for Racing Engines”
During the search for information for this article, we put the “bee” on Vic Edelbrock, manufacturer of Edelbrock speed equipment, to see what we could gain from his years of experience with the cooling problems of competition engines. As usual, Vic had all the answers and was more than happy to cooperate.
Vic began by discussing several factors of engine condition that can have a definite influence on the load carried by a cooling system. Lean fuel mixtures, for instance, resulting from carburetor metering jets of the wrong size, or from air leaks in the induction system, cause hotter than normal combustion temperatures and the transference of additional heat to the cooling system . Ignition timing that is too far advanced can cause detonation and increased cylinder temperatures. Retarded ignition timing fires the fuel in the cylinder when the pistons are on their way down on the power stroke and larger areas of the cylinder wall are exposed to combustion heat, thereby increasing heat transference to the cooling system. Late valve timing also exposes greater areas of the cylinder walls to combustion heat. Sharp edges, overhanging gaskets, and heavy carbon deposits in the combustion chambers can cause detonation and consequent high compression temperatures. Also, carbon deposits can act as an insulation between combustion gases and combustion chamber surfaces, increasing chamber temperatures and detonation tendencies. Spark plugs of a heat range hotter than that required can cause detonation.
Exhaust back pressure cause by obstructed exhaust passages, inadequate manifolds, frozen exhaust damper valves or clogged mufflers or tailpipes can prevent exhaust gases from escaping freely from the cylinders and increases the quantity of heat transfer to the cooling system. Exhaust passages sometimes become partially obstructed when a core breaks while the block is being cast--an obstruction of this type can be chipped out of the passage with a chisel.
Vic also discussed the subjects of correct cylinder head installation, which he considers one of the most important factors in the prevention of overheating; in-efficient water pumps; deteriorated water hoses; scale conditions, sometimes attributable to the addition of certain brands of stop leak to the system; pressure caps and their effect; thermostats and their action; and other subjects covered previously in this article.
The method of testing the soundness of cylinder walls and intake and exhaust passages in engine blocks that have been bored, ported, and relieved was demonstrated with the equipment used in Vic’s shop for this purpose. The equipment consists of a steel plate cut to fit the top of a cylinder block, with openings over the cylinders and around the valves, and an adaptor for connecting an air hose to the water inlet on the water pump. The block is checked by bolting the plate to the block with a suitable had gasket to seal water openings in the top of the block and then increasing the pressure in the water camber to 10 to 15 pounds per square inch with air from the air hose. With pressure in the block, leaks are readily located by applying a solution of soap and water to the cylinder walls and intake and exhaust passages with a brush. The detrimental effects of combustion leaks through the cylinder or passage walls have already been discussed; if any leaks are found that cannot be repaired, the block should be discarded.
Boring cylinders to large oversizes can add to overheating difficulties if the walls become so thin that they distort under pressure and permit combustion gases to blow by the rings and pistons. Engines assembled with inadequate clearances between their moving parts can create sufficient heat from internal friction to cause overheating.
Cooling System Modifications for Track Racing
Vic’s observations of cooling system improvements for Ford V8 and Mercury engines used for track racing proved to be especially interesting. At one time these engines were considered practically impossible to cool when used for track competition, but methods have since been devised whereby cooling troubles can be eliminated in practically all cases by making minor changes to the system.
A common fault of automotive engines converted for racing is the tendency of the water pumps to pump much more water at high speeds than is actually needed to cool the engine. When this occurs water is pumped out the radiator overflow because the water cannot flow through the radiator core as fast as it is pumped into the upper radiator tank. A Ford V8 or Mercury pump can be modified to reduce its pumping capacity by removing three of the six vanes from its impellor and drilling a 5/16 inch diameter hole in each remaining vane. The treatment doesn’t leave much of the impellor to circulate the water, but little is needed at high pump speeds. Then, too, the natural thermo-siphoning tendency of the hot water in the system to rise and flow toward the outlet in the cylinder heads is almost sufficient in itself to cool the engine. The thermostat in each cylinder should be left in place or replaced with a restrictor washer with a hole approximately 5/8 inch in diameter in the center. Restriction to water flow provided by thermostats or restrictor washers also aids in preventing water loss through the overflow pipe.
Water circulation through the cylinder blocks can be improved by blocking the upper two water holes in the center of the block directly over the center exhaust passage. Blocking these holes with thin piece of brass shim stock placed between the block and head gasket forces the water to travel to the rear section of the block before it can escape to the cylinder head. Circulation in late model Ford V8 and Mercury blocks has been modified along these lines by changes in head gasket design.
Best results have been had with radiator cores that provide the maximum possible frontal area. The design of the radiator shell will limit the size of the core that can be used, but full advantage should be taken of every available square inch of space. Core thickness of 3 to 3 ½ inches is considered the practical maximum for efficient cooling. Radiators should be installed so that hoses between the outlets fittings in the heads and the radiator inlets have at least a slight rise through out their length, with the radiator inlets above the engine outlets. If the radiator end of a hose is lower than the engine end, or if any part of the hose is higher than the outlet end, it is possible for a steam pocket to form at the high spot in the hose and effect circulation of the water.
The radiator should be situated that air flow through the core in not restricted. This shouldn’t pose too great a problem in cars built for track racing unless a fancy grille is used in the radiator shell. Vic found by experimentation that the installation of a seemingly plain grille over the radiator of his V8-60 midget raised the engine’s operating temperature 15 degrees, sufficient to mean the difference between a passable temperature and overheating.
Another of Vic’s discoveries was that ordinary window screen mounted on a suitable frame made a better “shaker” screen than the ¼ inch mesh hardware cloth ordinarily used. Shaker screens are mounted in front of the radiator when racing on dirt tracks to catch dirt and mud particles before they clog the radiators air passages. The screens are loosely mounted, or suspended on springs, so they can move in relation to the chassis and literally shake themselves clean while the car is moving. But despite the shaking action, dirt and mud have a tendency to become lodged in the mesh of the hardware cloth and stick, while the finer mesh window screen, by not having openings large enough for the mud to become lodged in, stays clean.
Vic mentioned something else that is often overlooked in track and lakes cars, and that is the fact that although many precautions are taken to get air through the radiator, many times a means is not provided for getting air out of the engine compartment after it has gone through the radiator. This means that the engine in a constant bath of heated air, and fresh air flow through the radiator is restricted by the air trapped in the engine compartment. The cure for a condition of this type is to ventilate the engine compartment by removing some of the sheet metal surrounding the engine or by cutting many louvers in the metal.
The wrong rear axle ratio for existing track conditions can cause engine overheating if it causes the engine to be lugged or over-revved. Ratio that is too high will overload the engine, while with a ratio that is too low, the engine will over-rev.
I keep a data base in my computer of flathead articles that have appeared in different hot rod publications from the past sixty-plus years. I remembered reading a story about installing restrictors and I was able to go into my data base and locate the article. In the October 1952 issue of Hot Rod Magazine there was a huge article on “How To Keep Your Engine Cool”, one section of the article was devoted to “Cooling Tips for Racing Engines”. I believe this article is the source of the restrictor myth. As this racing tip was past down from generation to generation of flathead enthusiasts somewhere along the way the part about it only being a modification for racing engines was omitted. Here is the racing part of the article, there is a lot of good info in it.
Jerry
“Cooling Tips for Racing Engines”
During the search for information for this article, we put the “bee” on Vic Edelbrock, manufacturer of Edelbrock speed equipment, to see what we could gain from his years of experience with the cooling problems of competition engines. As usual, Vic had all the answers and was more than happy to cooperate.
Vic began by discussing several factors of engine condition that can have a definite influence on the load carried by a cooling system. Lean fuel mixtures, for instance, resulting from carburetor metering jets of the wrong size, or from air leaks in the induction system, cause hotter than normal combustion temperatures and the transference of additional heat to the cooling system . Ignition timing that is too far advanced can cause detonation and increased cylinder temperatures. Retarded ignition timing fires the fuel in the cylinder when the pistons are on their way down on the power stroke and larger areas of the cylinder wall are exposed to combustion heat, thereby increasing heat transference to the cooling system. Late valve timing also exposes greater areas of the cylinder walls to combustion heat. Sharp edges, overhanging gaskets, and heavy carbon deposits in the combustion chambers can cause detonation and consequent high compression temperatures. Also, carbon deposits can act as an insulation between combustion gases and combustion chamber surfaces, increasing chamber temperatures and detonation tendencies. Spark plugs of a heat range hotter than that required can cause detonation.
Exhaust back pressure cause by obstructed exhaust passages, inadequate manifolds, frozen exhaust damper valves or clogged mufflers or tailpipes can prevent exhaust gases from escaping freely from the cylinders and increases the quantity of heat transfer to the cooling system. Exhaust passages sometimes become partially obstructed when a core breaks while the block is being cast--an obstruction of this type can be chipped out of the passage with a chisel.
Vic also discussed the subjects of correct cylinder head installation, which he considers one of the most important factors in the prevention of overheating; in-efficient water pumps; deteriorated water hoses; scale conditions, sometimes attributable to the addition of certain brands of stop leak to the system; pressure caps and their effect; thermostats and their action; and other subjects covered previously in this article.
The method of testing the soundness of cylinder walls and intake and exhaust passages in engine blocks that have been bored, ported, and relieved was demonstrated with the equipment used in Vic’s shop for this purpose. The equipment consists of a steel plate cut to fit the top of a cylinder block, with openings over the cylinders and around the valves, and an adaptor for connecting an air hose to the water inlet on the water pump. The block is checked by bolting the plate to the block with a suitable had gasket to seal water openings in the top of the block and then increasing the pressure in the water camber to 10 to 15 pounds per square inch with air from the air hose. With pressure in the block, leaks are readily located by applying a solution of soap and water to the cylinder walls and intake and exhaust passages with a brush. The detrimental effects of combustion leaks through the cylinder or passage walls have already been discussed; if any leaks are found that cannot be repaired, the block should be discarded.
Boring cylinders to large oversizes can add to overheating difficulties if the walls become so thin that they distort under pressure and permit combustion gases to blow by the rings and pistons. Engines assembled with inadequate clearances between their moving parts can create sufficient heat from internal friction to cause overheating.
Cooling System Modifications for Track Racing
Vic’s observations of cooling system improvements for Ford V8 and Mercury engines used for track racing proved to be especially interesting. At one time these engines were considered practically impossible to cool when used for track competition, but methods have since been devised whereby cooling troubles can be eliminated in practically all cases by making minor changes to the system.
A common fault of automotive engines converted for racing is the tendency of the water pumps to pump much more water at high speeds than is actually needed to cool the engine. When this occurs water is pumped out the radiator overflow because the water cannot flow through the radiator core as fast as it is pumped into the upper radiator tank. A Ford V8 or Mercury pump can be modified to reduce its pumping capacity by removing three of the six vanes from its impellor and drilling a 5/16 inch diameter hole in each remaining vane. The treatment doesn’t leave much of the impellor to circulate the water, but little is needed at high pump speeds. Then, too, the natural thermo-siphoning tendency of the hot water in the system to rise and flow toward the outlet in the cylinder heads is almost sufficient in itself to cool the engine. The thermostat in each cylinder should be left in place or replaced with a restrictor washer with a hole approximately 5/8 inch in diameter in the center. Restriction to water flow provided by thermostats or restrictor washers also aids in preventing water loss through the overflow pipe.
Water circulation through the cylinder blocks can be improved by blocking the upper two water holes in the center of the block directly over the center exhaust passage. Blocking these holes with thin piece of brass shim stock placed between the block and head gasket forces the water to travel to the rear section of the block before it can escape to the cylinder head. Circulation in late model Ford V8 and Mercury blocks has been modified along these lines by changes in head gasket design.
Best results have been had with radiator cores that provide the maximum possible frontal area. The design of the radiator shell will limit the size of the core that can be used, but full advantage should be taken of every available square inch of space. Core thickness of 3 to 3 ½ inches is considered the practical maximum for efficient cooling. Radiators should be installed so that hoses between the outlets fittings in the heads and the radiator inlets have at least a slight rise through out their length, with the radiator inlets above the engine outlets. If the radiator end of a hose is lower than the engine end, or if any part of the hose is higher than the outlet end, it is possible for a steam pocket to form at the high spot in the hose and effect circulation of the water.
The radiator should be situated that air flow through the core in not restricted. This shouldn’t pose too great a problem in cars built for track racing unless a fancy grille is used in the radiator shell. Vic found by experimentation that the installation of a seemingly plain grille over the radiator of his V8-60 midget raised the engine’s operating temperature 15 degrees, sufficient to mean the difference between a passable temperature and overheating.
Another of Vic’s discoveries was that ordinary window screen mounted on a suitable frame made a better “shaker” screen than the ¼ inch mesh hardware cloth ordinarily used. Shaker screens are mounted in front of the radiator when racing on dirt tracks to catch dirt and mud particles before they clog the radiators air passages. The screens are loosely mounted, or suspended on springs, so they can move in relation to the chassis and literally shake themselves clean while the car is moving. But despite the shaking action, dirt and mud have a tendency to become lodged in the mesh of the hardware cloth and stick, while the finer mesh window screen, by not having openings large enough for the mud to become lodged in, stays clean.
Vic mentioned something else that is often overlooked in track and lakes cars, and that is the fact that although many precautions are taken to get air through the radiator, many times a means is not provided for getting air out of the engine compartment after it has gone through the radiator. This means that the engine in a constant bath of heated air, and fresh air flow through the radiator is restricted by the air trapped in the engine compartment. The cure for a condition of this type is to ventilate the engine compartment by removing some of the sheet metal surrounding the engine or by cutting many louvers in the metal.
The wrong rear axle ratio for existing track conditions can cause engine overheating if it causes the engine to be lugged or over-revved. Ratio that is too high will overload the engine, while with a ratio that is too low, the engine will over-rev.
