how the cooling system works, basics

grumpyvette

Administrator
Staff member
READ THE LINKS, POSTED IN THIS THREAD and their sub links ALSO

Almost all engine combos run best, and have the least wear and emissions when your running a 180F-190F t-stat and the engine coolant temp stays in the 180F-210 f range, most of the time.
keep in mind a t-stat does not limit the cooler coolant entering the engine, its function is to keep the coolant flow through the engine minimized until its absorbed enough heat to reach the t-stats opening temp that allows the coolant to flow out of the engine.
oil temp should reach and at least occasionally exceed 215F to burn off moisture in the oil,and prevent acids forming in the oil,and anything over 190F and under about 240F on oil temp will be ok, with 210-215F about ideal.
carburetor equipped engine combos usually run best with a 180F t-stat, but occasionally a 160F t-stat will be better, keep in mind the t-stat only controls WHEN the radiator and water pump reach full flow rates, its the radiator and water pump, oil system, and oil pan config, that generally control the rate of heat exchange and engine temp. as they provide much of the heat transfer.
keep in mind the better synthetic oils reduce friction and that tends to reduce heat in the valve train, which is a significant source of engine heat.
and keeping the oil flow moving, absorbing and transferring heat in the engine tends to both increase durability and if you think about it cooling the rings, bearings,pistons and valve train will do a good deal towards reducing engine temperatures
Ive had good results with a 200F T-stat with the holes drilled (READ THE LINK) but many guys select a 180F t-stat.
its best to start planing an effective cooling system with some basic facts,
you'll want to have the largest surface area to maximize heat transfer from hot engine coolant to outside air flow as the physical clearances allow and your budget can support

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OK, lets think about the basics, theres several steps in the process ,an engine generates heat thru combustion and friction, oil flowing over the heated surfaces should lubricate and absorb and transfer a good deal of the heat to the oil, oil flowing over the block should help transfer heat to the coolant in the block.
obviously an oil cooler, if correctly sized and designed with a separate electrical fan can be used to reduce oil temps, and a 7-9 quart oil pan can act as a reservoir of engine oil , cooling the oil before its pumped back to the bearings and moving parts allows that oil to absorb more heat, during its trip thru the engine
most t-stats work by by having a thermo reactive wax that
starts to expand at a set temperature , then over about 10F-20F it continues to expand,and allow heated coolant to flow to the radiator, thus the t-stat will remain closed until its rated temperature range is reached and it will open wider up to its fully open position over about a 2-5 minute time frame


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the more surface area and coolant volume the radiator has the more potential it has to transfer heat to outside air flow

the shroud definitely helps cooling efficiency, SIGNIFICANTLY,if you don,t have one shop carefully and buy one , if your bucks down visit a salvage yard , measure carefully and buy one used they are commonly under $30
modify it as required to fit
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IN both the big block and small block engine in most configurations ,(the LT1-LT4 uses reverse flow where the heads get coolant first)
IN MOST CHEVY V8s COOLANT FLOWS in to the front of the lower block,from the two exit ports in the water pump,
these two pictures, below just point out common coolant flow routes
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where it separated into the two cylinder banks,where it travels along the cylinder walls,
once the lower blocks full, then coolant travels upward through the holes in the block deck into the heads where it travels ,
around the combustion chambers and under the valve train,where the majority of engine heat is produced, then it back forward ,
where the flow of coolant enters a forward intake manifold passage to reach the t-stat , there it recombines from from each bank, flows up through the t-stat and back into the upper radiator
thus rear intake manifold coolant ports, between the cylinder heads, have nearly no,or any effect or restriction to engine cooling, look at the diagram
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adding an aux oil cooler with its own electrical fan,and ideally a transmission fluid cooler with its own electrical fan, would significantly reduce the heat load on the radiator and engine coolant

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viewtopic.php?f=57&t=5607
obviously the number of tubes, the total amount of coolant in the radiator and the surface area of the fins effects the radiators ability to transfer heat efficiently to the out side air flow, but the coolant in a properly designed radiator is forced into constant and repeated turbulent contact with the metal surfaces of the tubing, which is a flattened oval with a high surface area to volume ratio, and if the fins surface area and the air flow rates thru the fins are set up correctly rapid transfer of the coolants heat to the outside air is easily achieved, and heat transfer to the fins and air flow is fairly rapid and efficient.
You occasionally hear someone suggest that without a T-stat coolant flow thru thee radiator is going to be too rapid to allow heat to dissipate, this is a myth, keep in mind if you slow coolant flow through the radiator youve also slowed coolant flow thru the block so the coolants forced to absorb more heat , which is more difficult as its already hotter. YOU can,t force coolant thru the radiator so fast that it wont allow the heat transfer with any normal automotive water pump, in a decent radiator, so the higher the rate of coolant flow the better, obviously you can,t effectively transfer heat unless theres a rapid flow of cooler air to absorb that heat so your fans and duct work are also critical to effective cooling.
on some cooling systems a t-stat is mandatory or the water pump can,t control coolant flow as efficiently.
problems will occur if the radiator coolant tubes fill with corrosion,if you fail to use antifreeze which contains anti corrosives or the tubes flowing coolant get plugged with debris or the radiator fins used to transfer heat to outside air, get clogged or bent your reducing air or coolant flow rates

viewtopic.php?f=57&t=5607
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NEXT theres the coolant in the block, radiator, and the water pump that moves the coolant thru the block, which is used to absorb and transfer heat to the radiator where air flow over the radiator surface is used to dissipate the heat to the outside air. and the fans and duct work are used to direct that air flow, effectively.
as a general rule, the larger the surface area of the radiator and the longer the coolant takes to flow thru the radiator the more of its heat can be transferred to the outside air, and the faster the air travels over the radiator surface, and the greater the volume of that air, the more heat it can absorb.
if you think about this process it should become obvious that the larger the radiator surface area is and the more air flow you can efficiently force thru the radiator the more heat can be transferred to the outside air flow.
the heat generated by an engine increases with the RPM and torque loads applied, because both friction and combustion heat loads generated tend too increase.
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a correctly designed and ducted radiator can direct a great deal of air over the radiator fins, to efficiently transfer heat from the coolant to the air flow. The thermostat is designed to limit and meter, the amount of that air cooled, coolant re-entering the engine, to maintain the desired operational temp range, ideally that means that the radiator can cool the coolant well below the thermostats opening temp limit , so it only opens and adds cooled coolant as required , to drop the engine temps, to the desired level allowing the thermostat to close until the engine heat again exceeds the thermostats opening threshold.
but as heat loads are increased the radiators ability to handle the increases must be available or heat levels with continue to rise.
a thermostat has little or no effect on the coolant temp once that coolant temp exceeds the thermostats opening temps , its purpose is to restrict and limit excess, cool coolant, from the radiator, entering the engine,and resulting in the engine running too cool.
once the thermostat has opened the radiators ability to transfer heat to the air must exceed the engines ability to generate heat, or it will rapidly over run the radiators ability to dissipate heat, and the engine heat will continue to increase



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there is a great deal more related info in these threads

https://www.dewitts.com/collections/corvette-aluminum-radiators

viewtopic.php?f=57&t=4230&p=11173#p11173

http://www.chevyhiperformance.com/techa ... index.html

http://www.familycar.com/Classroom/CoolingSystem.htm

http://www.crankshaftcoalition.com/wiki ... ing_system

http://www.familycar.com/Classroom/CoolingSystem.htm

http://www.circletrack.com/enginetech/c ... index.html

viewtopic.php?f=54&t=296

viewtopic.php?f=57&t=4230&p=13590&hilit=smaller+displacement#p13590

viewtopic.php?f=57&t=2756&p=14146&hilit=duct+shroud#p14146

viewtopic.php?f=57&t=6888&p=22453&hilit=radiator+fin+count#p22453


viewtopic.php?f=57&t=4701&p=19139&hilit=aluminum+radiator#p19139

http://www.ifitjams.com/radiator.htm

viewtopic.php?f=57&t=1540

viewtopic.php?f=57&t=755

http://www.circletrack.com/enginetech/c ... index.html

viewtopic.php?f=57&t=348

viewtopic.php?f=57&t=2140

http://www.2carpros.com/how_does_it_work/cooling.htm
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http://www.meineke.com/stuff_about_cars ... ooling.asp
https://durathermfluids.com/pdf/techpapers/pressure-boiling-point.pdf
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look thru, and read this linked info, the links help

Cooling system basics

ENGINES generate HEAT thru FRICTION and COMBUSTION, the combustion heat is about 60% of the heat, but many people don’t realize that the valve springs and valve train and bearings and associated friction also cause a significant percentage of the heat, and that OIL FLOW absorbs and transfers much of that heat to the engine block and oil pan sump, where that heats absorbed by the coolant or air flow around the engine and oil pan, or transferred to an oil cooler, and back to either the air flow or coolant and that it’s the oil, that in many cases protects and transfers heat from many of the hotter components like valves, bearings, piston rings, pistons and valve springs.
that hot oil running over and forming a protective, often pressurized film, between the moving parts prevents direct contact of metal parts, but that oil also absorbs heat and transfers it thru the engine where the COOLANT absorbs and transports the heat to the radiator, where its transferred to the air flow around , and under the car.
the longer the coolant remains in the radiator the more heat it can transfer to the air flow, so the larger the effective surface area of the radiator and the faster the air flow thru that radiator the more effective the heat transfer can be, thats one reason multi pass radiators, thicker radiator coil designs and more fins per inch of surface area and aluminum with its high thermal transfer rate is used, in better radiators.

It should be rather obvious that the FAN is used to PULL air in large quantity thru the radiator so that air can absorb and transfer heat from the coolant in the radiator to that air flow. radiator shrouds or duct work significantly add to the fans ability to pull air thru the radiator fins surface, increasing the ability to transfer heat to the air flow. And that the fan is necessary at lower speeds where pressure of the air in front of the car at low speeds is not sufficient to force enough volume of the air thru the radiator to remove/absorb heat from the coolant. Coolant is forced thru the passages in the heads and block to absorb and transfer heat to the radiator by the water pump, in a closed loop.
The thermostat is a temp. Activated gate that opens fully only after a pre- set temp. Level is exceeded so that the engine reaches and maintains a designed temp range.
What many people don’t know or under stand is that both the volume of coolant in both the radiator and engine and the flow rates of that coolant are critical to its efficient function.
Standard fans rotate and pull air thru the radiator in direct relation to the engine rpm level, but unfortunately the air friction loads go up, as rpms increase faster than the fans pump air effectively at some rpm levels.
Clutch fans are designed, in many cases to spin the fan mechanically from the crankshaft rotation, via, a belt drive that limits the rpms to the point where air resistance equals a fluid couplings friction levels, this allows the fan to work at low & mid rpms, but effectively slip as the loads on the blades from air friction become higher lowering the engines loss, compared to a direct drive fan.
FLEX fans accomplish a similar reduction in engine load rates thru a change in fan blade angle of attack due to a reduced effective, working surface area.
WATER tends to absorb and transfer heat slightly better than anti-freeze but it’s far more conductive to electrolysis and corrosion, so a 50%/50% mix is usually used in radiators to prevent engine damage.
IN a correctly set up engine the oil flow over the valve springs, bearings and rockers, absorbs and transfers a good deal of the engine heat and the use of an oil cooler for engine oil and a TRANSMISSION COOLER if you've got an automatic transmission can and does lower the heat loads on the coolant system. A baffled 7-8 qt oil pan can dissipate a great deal of the engines heat!
BTW one frequently overlooked factor, in cooling your engine or adding an additional oil cooler, is your alternator size,in amps and wiring the alternator correctly, if your running a 70amp-100 amp stock alternator and using electric fans to cool the engine,its not going to provide the power required to spin the fans nearly fast enough to cool the engine like a better 200 amp alternator can


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http://www.summitracing.com/parts/BRA-1888/ (standard)
http://www.summitracing.com/parts/BRA-1688/ (counter clock)

https://static.summitracing.com/global/images/chartsguides/a/aaz-55-11111.pdf

http://garage.grumpysperformance.com/index.php?threads/engine-water-pumps.832/#post-3768

http://garage.grumpysperformance.com/index.php?threads/engine-water-pumps.832/#post-3768

http://garage.grumpysperformance.com/index.php?threads/swivel-thermostat-housing.9489/

http://garage.grumpysperformance.com/index.php?threads/correct-thermostat.5607/#post-26544

viewtopic.php?f=57&t=149

http://www.s-10crewcab.com/~henryj/fans/fans.html

http://www.dakotadigital.com/index.cfm? ... zm_641.jpg
TESTING

viewtopic.php?f=54&t=2093

viewtopic.php?f=57&t=940
 
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grumpyvette

Administrator
Staff member
viewtopic.php?f=57&t=869

viewtopic.php?f=57&t=348

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C4 related info
http://shbox.com/1/4th_gen_tech2.html#radflush

BTW you might be amazed at the crud that CAN collect in a radiators fins over time, just driving on the street on paved roads
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tubes fill with crud and become partly or fully clogged over time

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mounting a fan like these two examples without the correct fan shroud can cost you easily 30% or more in cooling efficiency, enough to make a very noticeable difference in engine temps
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full shroud fans (below) are more efficient than a fan alone or partial shroud (above)
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the shroud definitely helps cooling efficiency, SIGNIFICANTLY,if you don,t have one shop carefully and buy one , if your bucks down visit a salvage yard , measure carefully and buy one used they are commonly under $30
modify it as required to fit
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cooling is basically the process of transferring heat efficiently from its source, to the outside air flow as rapidly as possible thru the process of oil and coolant flow absorbing and transporting the heat from the hotter components to the, outside air, the faster, and more efficiently the fluids can absorb, transfer and release that heat, and the greater the surface area, and conductivity between the hot fluids, and the larger the volume of those fluids, in the heat exchange areas and the higher the speeds of the outside airflow the more likely you'll be to reduce the heat generated in the hotter areas, increasing the volume of oil and coolant in the system helps, increasing the surface area of the radiator, or adding an oil cooler or transmission cooler that adds an additional heat transfer surface to bleed off that heat to the outside air or allow the oil to release heat thru other surfaces than the radiators trans fluid cooler section will help, as will, adding a larger capacity oil pan and oil cooler, simply because the oil does much of the heat transfer from the hottest components to the coolant, so anything you can do to reduce oil temperatures tends to help. oil in the oil pan is exposed to air flowing over the oil pans outer surface and that will generally reduce its temperature, so the larger the oil pan capacity the longer the oil tends to be exposed to that cooling effect, naturally a real oil cooler with an electric fan will work even better but you can use both in tandem
on the first generation small block Chevy the coolant is drawn from the lower radiator hose by the water pump, and forced into the front of the block where it travels along the cylinder walls then after all the areas filled it moves upward into the cylinder heads thru holes in the head gasket that were designed to be small enough, to slightly slow the flow upward into the heads where the coolant thats absorbed cylinder wall heat will reverse direction and travels forward into the forward , in the cylinder heads collecting more heat until it flows thru the forward intake manifold coolant ports that direct the coolant to the t-stat and from there to the upper radiator hose that allows the coolant to drain back as it flows and cools thru the radiator to the lower radiator hose to complete the cycle.
this route tends to sweep any trapped air out of the system but its not ideal because the cylinder heads produce most of the engine heat, so the route was reversed in the second generation LT1 small blocks to insure the cylinder heads operated a few degrees cooler to reduce the tendency to reach detonation heat levels

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your stock corvette has a rather marginal cooling system that can be significantly improved upon.
obviously your engines tune, air/fuel ratio and ignition timing have a large effect on your cars operation temperature,moving the coolant thru the block efficiently and allowing the heat to rapidly dissipate, to the outside air flow with an efficient large capacity aluminum radiator will greatly improve the cars cooling.
the stock radiator is barely adequate for an engine putting out significantly more power as more hp creates more heat.
a stock transmission cooler won,t keep up with an aftermarket high stall converter, if you drive the car hard either.
keep in mind that the standard C4 corvette uses a REVERSE rotation water pump, and its not a true high volume design, aluminum water pumps will reduce weight on the front of the car,so think about that when selecting a water pump


WATER PUMP
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a quality radiator will be made from aluminum and have large cross flow tubes, read thru the links below,
theres several dozen sources but the better brand names, tend to have a better quality product than the cheaper imported versions

RADIATOR
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OIL PAN & OIL COOLER
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TRANSMISSION COOLER
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many guys fail to realize that the combo of a high capacity baffled oil pan and an oil cooler can remove a great deal of your engine heat before the radiator, and coolant in the engine ever needs to start absorbing and transferring that heat to the outside air flow , ITS, high volumes of OIL FLOWING over the valve train and thru the bearing clearances and lubricating the rotating assembly , that is cooling many of the hotter components, and keeping that oil cool and flowing over those components is your first layer of defense on cooling the engine. its the volume of oil , and how effectively you keep the oil temps stable in the 210F-240F ranges and the quality and how well the oils filtered,more than the pressure that's important to your engines durability

heres some RELATED THREADS, with MUCH MORE DETAILED INFO

viewtopic.php?f=57&t=176

viewtopic.php?f=57&t=853

viewtopic.php?f=57&t=149&p=9344&hilit=+thermostat#p9344

viewtopic.php?f=54&t=3536

viewtopic.php?f=54&t=65

viewtopic.php?f=57&t=1540

viewtopic.php?f=57&t=755

viewtopic.php?f=57&t=832
 
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grumpyvette

Administrator
Staff member
BTW
for those guys thinking of swapping to an LT1 intake on a L98 engine,notice the first gen or standard sbc heads have coolant transfer ports that allow coolant to exit thru the intake manifold mounted t-stat

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notice the LT1-4 heads have NO COOLANT PASSAGES TO THE INTAKE, and the T-stat and radiator hose connects to the water pump on the later LT series REVERSE FLOW ENGINES
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lt1 cylinder heads don,t flow coolant thru the intake to the radiator like the earlier heads do, the water pump is the exit point for coolant flow.
If your going to build the later LT1-4 buy this book its well worth the price (usually $16-$20)
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http://www.grandsportregistry.com/lt1vslt4_intakes.htm
NOTICE THE STANDARD DESIGN HEADS HAVE WATER to INTAKE TRANSFER PORTS
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LT1 Reverse Flow Cooling System
By Scott Mueller.

One of the greatest features of the '92 and up Chevrolet LT1 engine is the reverse flow cooling system. In fact it is reverse flow cooling that is truly the key to the incredible performance of the modern LT1. Reverse flow cooling is vastly superior to the conventional cooling systems used on virtually all other engines. This is because it cools the cylinder heads first, preventing detonation and allowing for a much higher compression ratio and more spark advance on a given grade of gasoline. A fringe benefit is that cylinder bore temperatures are higher and more uniform, which reduces piston ring friction. Because of this new cooling system, the LT1 can easily meet ever increasing emissions standards with significant gains in power, durability, and reliability.

Conventional Coolant Flow:

In a conventional engine design, coolant enters the front of the block and circulates through the block's water jacket. The coolant is first heated by the cylinder barrels, and then hot coolant is subsequently routed through the cylinder heads and intake manifold before returning through the thermostat to the radiator.

Because the coolant from the radiator is first directed to the cylinder bores, they run at below optimum temperatures which increases piston ring friction. The heads subsequently get coolant that has already been heated by the cylinder block, which causes the heads to run well above optimum temperatures. The hotter cylinder heads promote detonation (spark knock) and head gasket failures. To combat the increased tendency to detonate, compression ratios has to be lowered and spark advance reduced, which significantly reduces engine power output and efficiency.

Besides promoting detonation, causing gasket failures, forcing reduced compression, spark advance, and significantly reduced power output, a conventional cooling system causes several other problems. Since the thermostat is on the exit side of the system, it does not have direct control over the cold coolant entering from the radiator. This is especially true when the thermostat first opens after reaching operating temperature. As the thermostat first opens allowing hot coolant to exit the engine, a rush of very cold coolant enters the block all at once, shocking the engine and causing sudden dimensional changes in the metal components. The extreme thermal shock experienced by the engine causes head gaskets and other soft parts to fail much more quickly.

Conventional cooling system design also allows isolated engine hot spots to occur, which lead to the generation of steam pockets and coolant foaming. Coolant which is full of air and foam reduces cooling system performance and can even lead to engine overheating.

LT1 Coolant Flow:

The LT1 is completely different since it uses reverse flow cooling. The incoming coolant first encounters the thermostat, which now acts both on the inlet and outlet sides of the system. Depending on the engine coolant temperature, cold coolant from the radiator is carefully metered into the engine. This allows a more controlled amount of cold coolant to enter, which immediately mixes with the bypass coolant already flowing. This virtually eliminates the thermal shock present in the old system.

After entering through one side of the 2-way thermostat (at the appropriate temperature), the cold coolant is routed directly to the cylinder heads first, where the combustion chambers, spark plugs and exhaust ports are cooled. Then the heated coolant returns to the engine block and circulates around the cylinder barrels. The hot coolant from the block re-enters the water pump, and hits the other side of the 2-way thermostat, where it is either re-circulated back through the engine or directed to the radiator, depending on temperature.

The main concept behind reverse flow cooling is to cool the heads first, which greatly reduces the tendency for detonation, and is the primary reason that the LT1 can run 10.5 to 1 compression and fairly significant ignition advance on modern lead-free gasoline. Reverse flow cooling is THE KEY to the Generation II LT1s increased power, durability, and reliability over the first generation smallblock engine.

Thermostats:

All LT1 engines utilize a special 2-way acting full bypass thermostat. This means that the thermostat regulates coolant flow both in to as well as out of the engine, while the bypass portion of the thermostat circuit supplies the water pump with a full flow of liquid coolant at all times. This is unlike a conventional engine thermostat, which only regulates coolant flow at the engine outlet, and which does not allow full flow through the water pump when the engine is cold and the thermostat is in bypass mode.

Both sides of the 2-way thermostat used in the LT1 are linked together, and a single wax pellet actuator operates the spring loaded mechanism at a pre-set temperature. When the designated temperature is reached, the wax pellet expands, opening the dual acting valve. All current LT1s come from the factory with a relatively low 180 degree temperature thermostat. Most conventional engines today use 195 degree thermostats in order to meet emissions specifications at the expense of power, durability, and reliability.

It is important to note that the 2-way thermostat is unique to the Generation II LT1 and is not interchangeable with older Chevrolet smallblock engines. This is particularly important if you decide to change to a colder 160 degree thermostat, make sure it is the proper dual acting type required by the modern LT1.

Additional LT1 Cooling System Improvements:

In addition to reverse coolant flow, there are several other improvements in the LT1 cooling system over conventional engines.

Dry Intake Manifold:

The LT1 has absolutely NO water running through the intake manifold! Conventional cooling systems have passages in the intake manifold which allow coolant to crossover from one side of the engine to the other. In the LT1, coolant crossover occurs in the water pump, which is also where the thermostat is located. Since there are no coolant passages in the intake manifold, a major source of leaks has been eliminated. Overall engine reliability is improved since an intake manifold leak allows coolant to enter the top of the engine which can quickly wipe out the camshaft, lifters, and other major engine components. Designing a dry intake manifold without either coolant passages or a thermostat housing also allows a much lower profile. The LT1 engine is 87mm (nearly 3.5 inches) lower than the previous L98 Corvette engine.

Gear Driven Water Pump:

One big problem with conventional cooling systems is the water pump, which simply cannot last a targeted minimum 100,000 mile reliability figure without experiencing leaking gaskets or seal failures. This has traditionally been caused by the excessive side loads placed on the bearings and seals of a conventional water pump through the belt drive mechanism. In the LT1 this problem is solved by driving the water pump directly via a spur gear driven by the camshaft sprocket. This results in a dramatically more reliable water pump that should easily last 100,000 miles or more.

Since the water pump is no longer belt driven, the vehicle will still be driveable even if the serpentine belt fails. This is a major safety factor as it allows one to drive the partially disabled vehicle to the nearest service center.

Steam Vents:

The LT1 has strategically placed steam vents at the back of both cylinder heads. Since the heads are the hottest part of the engine, pockets of steam can be more easily generated there. The steam vents are connected together by a crossover vent tube at the back of the heads, which directs any steam and a small flow of coolant to the front of the engine where it flows through the throttle body, warming it for improved cold weather performance. After passing through the throttle body, most of the steam is condensed back into liquid coolant and returned to the system.

In LT1 B/D-cars, coolant exiting the throttle body is passed directly into a pressurized coolant reservoir where any air remaining in the coolant is completely scavenged. In LT1 F-cars, coolant from the throttle body connects to the heater outlet via a vented "tee" connector, where any trapped air in the system can be bled off manually. Eliminating steam pockets and foam in the coolant allows for more uniform cooling system performance, preventing hot spots and potential overheating.

Reverse Flow Radiator:

Unlike a conventional cooling system, the thermostat coolant outlet is connected to the bottom of the radiator. This forces the coolant entering the radiator to push up through the radiator core and eventually emerge through the top radiator coolant outlet. This helps to eliminate air pockets in the radiator, and provides a more even distribution of cooling through the core and improving radiator efficiency.

Precision Machined Thermostat Housing:

The thermostat housing is a precision machined component that fits directly onto the top of the water pump without a gasket. Instead, an O-ring is used to seal the thermostat inside the housing. This precision design reduces the tendency for leaks, plus it makes thermostat replacement a very simple job since there is no old gasket material to scrape off. Servicing is further simplified because the thermostat housing is situated directly on top of the water pump, and access is unobstructed. I dare say that the LT1 thermostat is the easiest to change I have ever experienced. Finally, an air bleeder valve is located on the top of the thermostat housing, which allows one to quickly and easily bleed out any trapped air after cooling system maintenance has been performed.

Low Operating Pressure:

The entire cooling system on the LT1 is designed to operate at lower pressures than conventional cooling systems. The maximum operating pressure in the LT1 cooling system is 15 psi for B/D-cars and 18 psi for F-cars, limited by a pressure cap. These limits are similar to other cars, but in the LT1, these maximum pressures are rarely reached. Running at a lower pressure drastically decreases the number of leaks and significantly improves overall reliability and durability.

Coolant Reservoir:

Corvette and B/D-car LT1 applications use a pressurized coolant recovery reservoir instead of a non-pressurized overflow tank used with conventional cooling systems. All of the coolant flows continuously through the pressurized reservoir, which is an integral part of the cooling system. The pressurized reservoir in the LT1 B/D-cars is connected to the cooling system in three places. One inlet hose connects to the top of the RH radiator tank, a second inlet hose is attached through a "tee" connection on the heater inlet hose, and a third outlet hose is connected to a "tee" connection in the throttle body heater outlet.

The pressurized reservoir is mounted at the highest point in the system, and provides a place where all air can be continuously scavenged from the coolant. Any steam and bubbles are allowed to rise to the surface, eliminating foam and providing pure liquid coolant back to the engine. Pure liquid coolant is returned to the system via the heater outlet hose connection. The pressure relief/vent cap in these systems is rated at 15 psi and is located on the reservoir rather than the radiator.

LT1 F-cars use a conventional coolant recovery system which consists of a non-pressurized coolant overflow tank connected to the radiator by a single hose. These cars use an 18 psi rated pressure relief/vent cap on the radiator like most conventional systems. Since these cars cannot scavenge air from the coolant as well as the B/D-car or Corvette systems, they have two air bleeder valves for manually bleeding trapped air from the system. One is in the thermostat housing, which is the same as all other LT1 engine vehicles, and the second one is located in a "tee" where the coolant from the throttle body connects to the heater return hose.

B/D-car LT1 (Caprice/Impala/Roadmaster/Fleetwood) Cooling Systems:

Standard equipment for all LT1 equipped B/D-cars is a dual electric fan setup with a 150-watt primary (RH) fan and a 100-watt secondary (LH) fan. The electric engine coolant fans are independently operated by the PCM (Powertrain Control Module) based on the inputs from the Engine Coolant Temperature (ECT) sensor, A/C Pressure Sensor, Vehicle Speed Sensor (VSS), and various other inputs.

The B/D-car coolant fans operate under PCM control at the following engine temperatures and A/C system pressures:

Fan Mode
Temperature A/C Pressure
Primary (RH) Fan ON 107 C 225 F 189 psi
Primary (RH) Fan OFF 103 C 217 F 150 psi
Secondary (LH) Fan ON 111 C 232 F 240 psi
Secondary (LH) Fan OFF 107 C 225 F 210 psi

Additionally, the PCM will turn off the fans at higher vehicle speeds (above 48 MPH I believe) since running fans can actually impede airflow through the radiator at high
speed. Each fan also has a minimum running time. Once activated, the primary fan will run for a minimum of 50 seconds, and the secondary fan for a minimum of 26
seconds. Finally, certain Diagnostic Trouble Codes (DTCs) may cause the PCM to turn on one or both fans.

All LT1 B/D-cars have two transmission oil coolers and an engine oil cooler as standard equipment. The transmission coolers include a primary oil to water type inside the RH radiator tank, and a secondary external oil to air cooler (KD1) mounted in front of the radiator on the RH side. The external KD1 cooler is an aluminum stacked plate type cooler painted black with metal tube lines linking it in series with the other cooler in the radiator tank. LT1 B/D-cars also include an engine oil to water cooler (KC4) mounted in the LH radiator tank.

Optional B/D-car LT1 Cooling Systems:

There are two optional cooling system upgrades for LT1 B/D-cars, called V03 (Extra Capacity Cooling), and V08 (Heavy Duty Cooling). Performance models such as the WX3 (Impala SS) and 9C1 (Police) cars automatically get the upgraded V03 (Extra Capacity Cooling) system. V03 includes a larger radiator, an increased capacity A/C condenser, and an upgraded secondary electric fan. V03 is also optional on most B/D-car models.

Note that the '94 V03 (Extra Capacity Cooling) option uses a 150-watt primary (RH) fan, and an upgraded 240-watt secondary (LH) fan. In '95-'96 the V03 package was revised and no longer included an upgraded 240-watt secondary fan. Instead the standard 100-watt secondary fan was used, which is the same as the base cooling system.

B/D-cars other than the Impala SS or Police package Caprice also have an optional V08 (Heavy Duty Cooling) package which is part of the V92 (Trailer Towing) package. V08 includes the larger radiator, increased capacity A/C condenser, and upgraded secondary fan as in the V03 system, however it differs in the primary cooling fan. With V08 the 150-watt electric primary fan is replaced by a mechanical belt driven thermostatic clutch fan. To drive the mechanical fan, the V08 system includes a crank pulley, belt tensioner and bracket, and a large radiator shroud in addition to the mechanical fan itself. This package is not available on the WX3 (Impala SS) or 9C1 (Police) cars since the mechanical fan is driven by an additional pulley and belt on the engine crankshaft, which draws engine power thus reducing performance.

The mechanical fan used with the V08 cooling system contains a built-in thermostatic clutch which senses the temperature of air that has been drawn through the radiator. When the temperature of this air is below 66 degrees C (151 degrees F), the clutch freewheels and limits the fan speed to 800-1,400 rpm. When the temperature rises above 66 degrees C (151 degrees F), the clutch begins to engage, and the fan speed increases to about 2,200 rpm. The RH radiator hose in V08 equipped vehicles has a steel tube section near the fan designed to prevent damage in case of fan contact.

There are several SEO (Special Equipment Option) B-car cooling options which are included as standard only with 9C1 (Police) package Caprices. These include the following:

In addition to the standard inclusion of the V03 (Extra Capacity Cooling) package, all LT1 Caprice 9C1 (Police) cars also include SEO 1T1 (Silicone Radiator and Heater Hoses). SEO 1T1 consists of special green radiator and heater hoses made out of pure silicone rubber. These hoses are designed to last the life of the vehicle and never need replacement unlike the standard black rubber hoses. SEO 1T1 also includes heavy duty stainless steel worm gear hose clamps which replace the standard squeeze type hose clamps. The clamps have a solid full perimeter band, which prevents the hose from extruding between the slotted area where the screw fits. This also prevents the hose from being cut or damaged by the clamp, and allows a more even sealing force around the entire clamp perimeter.

The 9C1 Police package also includes SEO 7P8 (External Engine Oil to Air Cooler). This is an unpainted aluminum stacked plate type cooler which is mounted in front of the radiator on the LH side opposite the external transmission cooler. This heavy duty engine oil cooler replaces the standard engine oil to water cooler found in the LH radiator tank of other LT1 B-cars.

Also included with the Police package is SEO 7L9 (Power Steering Fluid Cooler). This consists of a loop of metal tubing installed between the radiator lower support and the front stabilizer bar. This cooler prevents the power steering fluid from overheating in rigorous driving situations such as high speed persuit.

F-car LT1 (Camaro/Firebird) Cooling Systems:

Standard equipment for all LT1 F-cars with A/C is a dual electric fan setup with primary (LH) and secondary (RH) fans. There are two different wiring schemes used for these fans, an early design that was used in '93-'94 and a late design that has been used from mid-'94 up. Note that non-A/C F-cars have a single primary fan which operates at a fixed high speed.

In '93 and early '94 models with A/C, the two cooling fans are independently operated by the PCM (Powertrain Control Module) at a high fixed speed by using a single relay for each fan. Late '94 and newer F-car models operate both fans simultaneously in either a low or a high speed mode by using 3 relays. In low speed mode, the fans are powered in series. In high speed mode, the relays operate to power both fans in parallel, resulting in a higher speed of operation.

One way to tell which setup you have is by looking at the alternator. If an F-car is equipped with the 124 amp alternator (KG7), then the vehicle has the early design setup and the fans are operated independently. If the vehicle has the 140 amp alternator (KG9), then it also has the newer design configuration which operates the fans simultaneously in low or high speed modes.

The PCM operates the coolant fans based on input from the Engine Coolant Temperature (ECT) sensor, A/C Pressure Sensor, Vehicle Speed Sensor (VSS), and various other inputs. The F-car coolant fans operate at the following temperatures and pressures:

Fan Mode
Temperature A/C Pressure
Primary (LH) or Dual Low-speed Fan(s) ON: 108 C 226 F 248 psi*
Primary (LH) or Dual Low-speed Fan(s) OFF: 105 C 221 F 208 psi*
Secondary (RH) or Dual High-speed Fan(s) ON 113 C 235 F 248 psi
Secondary (RH) or Dual High-speed Fan(s) OFF: 110 C 230 F 208 ps

*Note - this information is probably incorrect, although it is quoted from the service manual.

Additionally, the PCM will turn off the fans at higher vehicle speeds (above 70 MPH I believe) since running fans can actually impede airflow through the radiator at high speed. Each fan or fan mode has a minimum running time. Once activated, the primary fan or dual low-speed fans will run for a minimum of 50 seconds, and the secondary or dual high-speed fans for a minimum of 30 seconds. Finally, certain Diagnostic Trouble Codes (DTCs) may cause the PCM to turn on one or both fans.

All LT1 F-cars with automatic transmissions also have a transmission oil cooler as standard equipment. The transmission cooler is an oil to water type mounted inside the RH radiator tank.

Optional F-car LT1 Cooling Systems:

There is only one option in an LT1 F-car with respect to cooling, and that is an engine oil cooler (KC4). The engine oil cooler is an oil to water design that is mounted in the LH radiator tank. The KC4 oil cooler is included with various other combinations of options on the F-cars.

Operating Characteristics and Observations:

I have an accurate digital temperature gauge installed in the RH cylinder head water jacket on my '94 Impala SS. I installed a brass "T" fitting in the RH cylinder head, in the tapped hole where the factory temperature gauge sender was originally installed. This allowed me to install both the original analog gauge sender as well as the sender for the new digital gauge. With the stock 180 degree thermostat, cruising at 80 mph on a cool night I would routinely measure coolant temperatures in the head as low as 167 degrees! If I slowed down, the temperature would climb up into the 170-180 degree range depending on ambient temperatures and cruising speed. The temperature would run in the 180s-190s cruising more slowly on a hot summer day. In heavy stop and go traffic, the temperature would quickly climb up into the 220-230 degree area, which is where the primary fan starts to come on.

Many have noticed as I have that the engine will actually run cooler in traffic with the A/C on. This is because turning on the A/C will also cause the PCM to activate at least the primary fan, and possibly the secondary fan (depending on A/C system pressure) as well.

The radiator and A/C condenser in B/D-cars equipped with the RPO (Regular Production Option) V08 (Heavy Duty Cooling) or V03 (Extra Capacity Cooling) systems are extremely large, perhaps the largest of any passenger car on the market today. The cooling and A/C system performance on these cars are outstanding, in fact the best I have seen on any vehicle.

Recommendations for Cooling System improvements:

If you have a B/D-car, there are several easy improvements you can make by simply adding the cooling related SEOs (Special Equipment Options) from the 9C1 Caprice Police package. For example, I have installed all of the Police package cooling upgrades in my '94 Impala SS. This includes the 1T1 silicone hoses, 7L9 power steering fluid cooler, and 7P8 external engine oil cooler. Combined with the already powerful V03 cooling system, these factory upgrades combine to form the most extreme duty factory cooling system present on any automobile I have seen.

If you have an F-car which was not factory equipped with the optional KC4 engine oil cooler, then I would highly recommend installing it as an upgrade. The KC4 option consists of a different radiator with the engine oil cooler located inside the LH tank. An adapter installs on the oil filter pad between the filter and the engine, and lines run to the cooler in the radiator tank.

There are two other cooling system improvements that can be applied to any vehicles with the LT1 engine, including the Corvette and F-cars (Camaro/Firebird). These are to change to a colder 160 degree thermostat (180 is standard), and to alter the electric cooling fans to come on at a lower temperature. This latter function can be accomplished by adding an external thermostatic switch to the fan circuit, or by re-programming the PCM fan operation settings.

As mentioned earlier in this article, the stock fans do not come on until at least 225 degrees, which I feel is too hot. To prevent the engine from heating up this high in traffic or while moving slowly, I installed a 203 degree GM thermostatic switch (p/n 3053190) in a pre-existing tapped hole in the LH cylinder head water jacket, and wired it to both the primary and secondary fan relay via a 3-position toggle switch.

When the coolant temperature reaches 203 degrees, the primary or secondary fan (depending on the setting of the toggle switch) will run. This prevents the engine from running hotter than about 200 degrees or so. I have tested this modification in 100 degree ambient temperatures, while trapped in stop and go traffic, and never saw coolant temperatures higher than 205 degrees. I wired the toggle switch to operate either the primary or secondary fan, as well as to disconnect the thermostatic switch from the circuit, thus disabling this function. No matter what the toggle switch setting, the PCM still has control over the fan relays, and will continue to operate the fans oblivious to the additional thermostatic switch function.

I have more recently purchased the Hypertech Power Programmer, which re-programs the PCM to turn the primary fan on at 176 degrees (instead of 225), and the secondary fan on at 191 (instead of 232). At first I installed the Hypertech program without the recommended 160 degree thermostat in order to observe the operation of the fans. I found that the primary fan would run continuously once the engine had warmed up, and even the secondary fan would be on most of the time. This is due to the overlap between the high thermostat setting and the lower fan activation temperatures programmed in by Hypertech. The new settings were turning the primary fan on at a setting lower than the thermostat itself would open.

After installing the recommended 160 degree thermostat, the fans worked normally, and would only begin to run after the car was not moving which allowed the temperature to rise. In actual operation I saw temperatures while moving about 10 degrees lower than what I observed with the 180 degree thermostat. While moving very slowly or sitting stationery, the engine would never climb above the low 190 range, no matter how high the ambient temperatures was or how slow I was moving. After observing this operation, I would wholeheartedly recommend the 160 degree thermostat and the Hypertech Power Programmer. If you use the Power Programmer, then the 160 degree thermostat MUST be installed or the fans will run continuously, which is not good for either the fans, alternator, or battery.

If you do not want to purchase the (fairly expensive) Power Programmer, then I highly recommend installing the 203 degree thermostatic fan switch I listed, which will prevent the excessive temperatures encountered in traffic that are allowed by the stock PCM program settings. The fan switch will work well with either the stock 180 degree thermostat or a 160 degree unit, and will limit the maximum coolant temperatures to 205 degrees or less.

GM Vehicles Featuring the Generation II LT1:
Chassis Models Years
Y-car Corvette '92-'96
F-car Camaro/Firebird '93-'96
B-car Caprice/Impala/Roadmaster 94-'96
D-car Fleetwood '94-'96
 

grumpyvette

Administrator
Staff member
to start the improvements to cooling the cars engine you need to think thru the sources of engine heat and how to, lower the temperatures or how to absorb and transfer that heat to the outside air flow effectively
a large efficient aluminum radiator, and a high volume water pump are a good place to start, adding a 7-8 quart baffled oil pan and a transmission cooler if your running an automatic transmission will also tend to lower engine temps. and adding a slightly higher capacity aluminum transmission pan sure won,t hurt either.
and drilling the t-stat flange with 6-8 1/8" holes helps a surprising amount on most corvettes.
keeping the fins in the radiator free of trash and the duct work sealed so airflow is directed thru the radiator helps, and adding a more efficient fan to both the pull and push side of the radiator sure won,t hurt.
keep in mind its OIL FLOW that does much of the cooling on the hotter components, so an OIL COOLER , and a HIGH CAPACITY BAFFLED OIL PAN,will go a long way to dropping engine temps, and if the car tends to over heat in traffic one old trick is to turn on the cars heater, while that doesn,t help the driver much it bleeds a significant amount of heat from the cars coolant temps.

http://forum.grumpysperformance.com...]http://www.summitracing.com/parts/DER-16749/

http://www.summitracing.com/parts/SUM-890015/

http://www.summitracing.com/parts/PRM-18907/
 

grumpyvette

Administrator
Staff member
lots of good suggestions above!
stock radiators are pathetic at best, a quality aftermarket radiator with dual 1" tubes will work much better.
but don,t forget that on automatic transmission cars a good deal of the radiator capacity is used cooling trans fluid,and engine oil, adding a separate transmission fluid and engine oil cooler reduces the heat loads on the radiator significantly
I've tested water wetter in several engines, its always resulted in at least a few degrees lower coolant temperatures, if you really want to reduce engine temps install a decent fan equipped oil cooler designed for a 24,000 lb truck with AN #8 line size, and ideally have a radiator with at least 2 square inches of frontal area per hp.
and yes youll rapidly find you require a larger radiator or one thats several inches thicker for greater surface area.
http://www.dewitts.com/

http://www.summitracing.com/parts/BCI-60046/

http://www.summitracing.com/parts/PRM-13311/

http://www.stl-vettes.com/65Vette/corvette_Misc/Images/Fan_Clutch_Adjust.pdf
prm-13311.jpg


http://forum.grumpysperformance.com/viewtopic.php?f=57&t=149&p=183#p183

http://forum.grumpysperformance.com/viewtopic.php?f=57&t=755

cooling is basically the process of transferring heat efficiently from its source, to the outside air flow as rapidly as possible thru the process of oil and coolant flow absorbing and transporting the heat from the hotter components to the, outside air, the faster, and more efficiently the fluids can absorb, transfer and release that heat, and the greater the surface area, and conductivity between the hot fluids, and the larger the volume of those fluids, in the heat exchange areas and the higher the speeds of the outside airflow the more likely you'll be to reduce the heat generated in the hotter areas, increasing the volume of oil and coolant in the system helps, increasing the surface area of the radiator, or adding an oil cooler or transmission cooler that adds an additional heat transfer surface to bleed off that heat to the outside air or allow the oil to release heat thru other surfaces than the radiators trans fluid cooler section will help, as will, adding a larger capacity oil pan and oil cooler, simply because the oil does much of the heat transfer from the hottest components to the coolant, so anything you can do to reduce oil temperatures tends to help. oil in the oil pan is exposed to air flowing over the oil pans outer surface and that will generally reduce its temperature, so the larger the oil pan capacity the longer the oil tends to be exposed to that cooling effect, naturally a real oil cooler with an electric fan will work even better but you can use both in tandem

you might be surprised at what a high capacity oil pan can do to reduce engine temperatures

21312_draw2.jpg
21312_draw1.jpg

well I'll assume you previously read the links on engine building,and quench, and you have at least tried to build a well balanced combo with reasonable quench,and tried to match the cam duration and lsa to the engines compression and intended power range, and you selected a fairly well matched cam timing and reasonable compression, but at this point in the tuning ,your still having indications your getting into detonation.
keep in mind that keeping reasonably consistent and as low as practicable , combustion chamber temps are a huge factor in avoiding detonation issues, having an auxiliary oil cooler and a trans fluid cooler with a powered fan, and the proper fuel/air ratio and ignition advance curve along with matching your cars engine dynamic compression ratio to the available fuel octane can go a long way toward avoiding detonation issu
Octane_Requirement.gif

so what your trying to do is reduce combustion chamber temps,increase your fuels octane, reduce your fuel/air temperatures, or reduce your combustion chamber pressure or speed up combustion
 
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grumpyvette

Administrator
Staff member
IF your wondering whats the difference in temperature of engine coolant between top and bottom of radiator, it should be rather obvious that the size and efficiency of both the engine developing the heat load and the cooling system transferring that captured and transported heat load, heat from the coolant transferred to the outside air flow will vary a great deal, with surface area coolant volume, coolant flow rates, fin surface area number of coolant passages and their design.Id also point out that few places will you find it mentioned that an auxiliary oil cooler with a fan and oil cooling radiator , and a 7-9 quart baffled oil pan can have easily lowered many engine operating temps 10F-15F degrees by their effect on transfer of engine heat alone ,as oil does a good deal of the actual heat absorption and transfer internally in an engine , reducing the heat load the coolant must transfer tends to lower the coolant peak temps, adding a transmission fluid cooler separate from the radiator can further reduce the coolant heat loads

most t-stats work by by having a thermo reactive wax that starts to expand at a set temperature , then over about 10F-20F it continues to expand,and allow heated coolant to flow to the radiator, thus the t-stat will remain closed until its rated temperature range is reached and it will open wider up to its fully open position over about a 2-5 minute time frame

wpan3.jpg

11-120.jpg

der-13720_w.jpg

Pressure

Higher system pressures raise the vapor point of the coolant and subsequently it's ability to absorb heat. A system pressure of 12-17 PSI results from the expansion of the coolant and trapped air going from
ambient temperature to operating temperature.

The system achieves this pressure only when the system is filled cold. When a warm system is opened and resealed this pressure is not obtainable because the coolant and trapped air are already expanded
when the system is sealed.

A Schrader valve installed in the system will allow the system to be charged by an air hose. This allows an already warm system to achieve operating pressure and minimizes the effect of trapped air in a cold system.

The fill cap must be the highest point of the system. Surge tanks must be used if the top of the radiator is not the highest point.

Trapped air seeks the highest point. A new system always has trapped air.
Always fill the surge tank completely, when the system reaches operating temperature it will expel any excess water out the overflow.

Placing a fill cap in the top radiator hose subjects the cap to the pressure drop of the top hose and the radiator core in addition to the system pressure. This can lower the effective pressure of a
22 PSI cap to as low as 2 PSI.

The vapor point of water increases under pressure as follows:

10 PSIG = 239 F

20 PSIG = 259 F

30 PSIG = 273 F

40 PSIG = 286 F

50 PSIG = 297 F

60 PSIG = 307 F

70 PSIG = 316 F

Always use the highest pressure cap available. It merely serves as safety valve
that has no function when the system is operating properly.
related linked info

http://www.rxauto.com/demo.htm


image010.jpg


http://garage.grumpysperformance.com/index.php?threads/how-radiator-caps-work.7718/


http://www.enginebasics.com/Advanced%20 ... rison.html

http://www.arrowheadradiator.com/14_rul ... obiles.htm

http://garage.grumpysperformance.com/index.php?threads/what-coolant-temp-is-correct.16201/

http://www.aa1car.com/library/tstemp.htm

http://www.xtrememotorworks.com/Cooling.htm
 
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