http://en.wikipedia.org/wiki/Wax_thermostatic_element
http://oljeep.com/rad/edge_radiator.html
http://www.stant.com/index.php/english/products/consumer-products/thermostats/faqs/
www.stewartcomponents.com
WHEN DOES A THERMOSTAT START TO OPEN?
The thermostat starts to open at the rated temperature, plus or minus 2 degrees (F).
Stant P/N 10330 16-lb Lev-R-Vent Radiator Cap
As you can see from the above and below diagrams, the radiator cap is a pressure relief valve used too relieve pressure and release excessive coolant overflows into a reservoir tank, and also to return the lost fluid from that reservoir tank back into the closed loop system, when the coolant and temps lower and the pressure drops inside of the radiator.
From Stant's website:
WHEN DOES A THERMOSTAT START TO OPEN?
The thermostat starts to open at the rated temperature, plus or minus 2 degrees (F).
WHEN IS A THERMOSTAT FULLY OPEN?
The thermostat is usually fully opened at 15 - 20 degrees (F) above the opening temperature.
I use a Stant P/N 10330 16-lb Lev-R-Vent Radiator Cap as shown above to further pressurize the coolant to raise the boiling temperature. It also helps provide backpressure on the impeller blades, thus helping to prevent cavitations, a very nasty occurrence.
For every lb of pressure that you impose on the radiator tank, the temperature that the coolant will reach before boiling will be raised by 3° F. So a 16 lb radiator pressure cap will raise the boiling temperature of the water by 48°F from 212° F, which is the normal sea level boiling point of water, to 260° F. This becomes significant due to the fact that if a vehicle looses any coolant, due to boil over and overflow, the system cannot cool down until that coolant, or additional coolant, is replaced back into the system, or until the vehicle is shut down and allowed to cool.
WHEN IS A THERMOSTAT FULLY OPEN?
The thermostat is usually fully opened at 15 - 20 degrees (F) above the opening temperature.
How does a thermostat work?
"Usually located within a metal or plastic housing where the upper radiator hose connects to the engine, most of today’s thermostats utilize the "reverse poppet" design, which opens against the flow of the coolant. Thermostats have a wax filled copper housing or cup called a "heat motor" that pushes the thermostat open against spring pressure.
keep in mind the main function of a T-stat is to RESTRICT coolant flow UNTIL the coolant temperature reaches and very slightly exceeds its designed temp level, at which point it opens to un-restrict the coolant flow,
now drilling a couple 3/32" holes in the flange INSURES that the t-states fully engulfed in coolant , where a t-stat without the holes may and in many cases will delay the t-stat opening because only static/ stationary mass of coolant temporarily trapped behind it can trigger its temp sensitive function.
As the engine's coolant warms up, the increase in heat causes the wax to melt and expand. The wax pushes against a piston inside a rubber boot. This forces the piston outward to open the thermostat. Within 3 or 4 degrees F. of the thermostat preset/rated temperature which is usually marked on the thermostat, the thermostat begins to unseat so coolant can start to circulate between the engine and radiator. It continues to open until engine cooling requirements are satisfied. It is fully open about 15-20 degrees above its rated temperature. If the temperature of the circulating coolant begins to drop, the wax element contracts, allowing spring tension to close the thermostat, thus decreasing coolant flow through the radiator. "
"While the thermostat is closed, there is no flow of coolant in the radiator loop, and coolant water is instead redirected through the engine, allowing it to warm up rapidly while also avoiding hot spots. The thermostat stays closed until the coolant temperature reaches the nominal thermostat opening temperature. The thermostat then progressively opens as the coolant temperature increases to the optimum operating temperature, increasing the coolant flow to the radiator. Once the optimum operating temperature is reached, the thermostat progressively increases or decreases its opening in response to temperature changes, dynamically balancing the coolant re-circulation flow and coolant flow to the radiator to maintain the engine temperature in the optimum range as engine heat output, vehicle speed, and outside ambient temperature change. Under normal operating conditions the thermostat is open to about half of its stroke travel, so that it can open further or reduce its opening to react to changes in operating conditions. A correctly designed thermostat will never be fully open or fully closed while the engine is operating normally, or overheating or over cooling would occur."
you might want too keep in mind that is the constant bath of oil flow that cools ,and lubes the hotter moving component parts, like the piston rings, and bore walls ,valves, valve guides, valve springs, cam,lobes lifters , basically the whole valve train , rockers , the bearings and all moving parts, the constant oil flow transfers that absorbed heat to the cylinder block surfaces and oil pan where coolant in the block and air flow around the engine absorb and transfer that heat to the outside air flow around the car.
While its true that a good deal of heat from combustion exits with the spent exhaust gasses, many people fail to realize that its that constant bath of pressurized oil flow , that circulates constantly through the engine, that forms a surface barrier between moving surfaces that does a great deal of the engine heat transfer and initial cooling, thus its the lubrication system working in conjunction with the cooling system that has a pronounced and vital effect on the engines cooling efficiency.
engine oil temps generally will run 10F-25F higher than coolant temps, partly because its OIL flow that absorbs and transfers much of the engine heat first.
This is also why adding an efficient oil and/or transmission fluid cooler tends to lower engine operation, and coolant temps.
related info
http://garage.grumpysperformance.com/index.php?threads/oil-system-mods-that-help.2187/
http://garage.grumpysperformance.com/index.php?threads/basic-info-on-your-v8-lube-system.52/
http://garage.grumpysperformance.com/index.php?threads/bearings-and-oil-flow.150/
http://garage.grumpysperformance.com/index.php?threads/which-oil-what-viscosity.1334/
http://garage.grumpysperformance.com/index.php?threads/valve-spring-cooling-via-engine-oil.6491/
http://garage.grumpysperformance.com/index.php?threads/heat-factor-questions.10955/#post-64430
http://garage.grumpysperformance.com/index.php?threads/thoughts-on-cooling.149/#post-58196
http://garage.grumpysperformance.co...y-in-building-a-good-engine.11682/#post-54682
http://garage.grumpysperformance.co...-custom-wet-sump-oil-pan.65/page-3#post-52146
http://garage.grumpysperformance.co...l-cooler-increases-durability.176/#post-48374
http://garage.grumpysperformance.co...ans-cooler-on-a-c4-corvette.10514/#post-44478
In an ideal world your coolant temp never exceeds 210F and spends most of its time around 180F-190F ,the key of course is having a cooling system that can easily transfer heat from the engine coolant to the outside air flow passing thru the radiator ,much faster than the engine can generate that heat.
WATCH THIS QUICK VIDEO
If your engines cooling system can,t transfer heat to the outside air flow , once the t-stats open, at a significantly faster rate than the engine can generate heat all the changes in the thermostat you care to make are a waste of time and effort.
oil MUST reach 215F occasionally during your cars operation, to burn off moisture and acids but should be at about 10 degrees hotter than the coolant, most good quality oil easily handles 240F for limited times,
A good oil cooler, and transmission fluid cooler can significantly reduce the heat load the radiator and engine coolant needs to deal with.
If I was you, and driving a chevy V8 performance car, Id stick a 180F- or -190F T-stat in the car, with several holes, ID custom drill in the flange, to allow some coolant flow at all times, this does slow the time required for the engine to reach operational temps but it also tends to almost totally reduce the temperature swings as the t-stat opens and closes
buy a new 180F- 190F t-stat, but before installing it drill 6 3/32" holes in the flange, this mod to the t-stat usually prevents that problem of having the t-stat constantly cycle and results in stable temps, the drilled holes will always allow a significant coolant flow rate,and prevents any chance of insulating air trapped around the t-stat from delaying it opening, but won,t generally allow full potential coolant flow , until the t-stat opens at operating temps so the engine will take longer to reach operating temps but the opening and closing cycles have much less effect on the engine temps. The net result is that your engine rarely goes much more than 10-15 degrees above the t-stat rated temp.... Ive consistently found that drilling the holes in the t-stat tends to make the temperatures more consistent and a bit cooler.
If you have a correctly set up radiator and cooling fans and duct work, the cooling system without a t-stat will stay at a lower temp than would be ideal, the t-stat maintains a minimum temp level, the holes don,t really effect this as you can,t get full flow until the t-stat opens but they do have a real tendency to keep the temp very consistent, Ive found a 190F to work best in most performance cars.
KEEP IN MIND THE THERMOSTATS JOB IS SIMPLY TO REDUCE THE FLOW OF COOLANT REACHING THE RADIATOR UNTIL the coolant reaches the t-states rated opening threshold temp, if its operating correctly it opens at that point and has little other effect on coolant flow, unless the coolant temp drops to the point it re-closes, you'll occasionally find a t-stat that restricts flow because its not fully opening but thats really not all that common, most either work or fail completely
the t-stat controls the minimum coolant temp but has little effect on coolant temp, once thats exceeded, if your cooling systems functioning correctly.
Ive had good results with a 200F T-stat with the holes drilled (READ THE LINK) but many guys select a 180F t-stat
http://www.ecklerscorvette.com/corvette ... -1996.html
If your corvette runs a bit hot, your sensors should turn on your fans at about 226F or if the air conditioners on, if the cars stock. but you have options and can get sensors that turn on the fans at lower temps like 180F, check your cooling fans are coming on and your coolant and oil levels are correct, and don,t forget to check the hot trans fluid level as in most application hot trans fluid adds a good deal of heat load to the radiator, keep in mind your ignition timing and advance curve effects the engine temps. as will potential vacuum leaks, your fuel/air ratio and other factors
http://www.summitracing.com/parts/vta-11190-vus
http://www.summitracing.com/parts/prf-30111/overview/
viewtopic.php?f=57&t=853
viewtopic.php?f=57&t=149
RADIATOR THERMOSTATS, OPEN a DESIGNED amount at a DESIGNED TEMPERATURE RANGE
RADIATOR THERMOSTATS,open and ALLOW greater flow more as the engine rpms INCREASE DUE to BOTH more combustion cycles adding heat per minute and greater water pump efficiency as rpms increase
NOTICE YOU GENERATE ENGINE HEAT IN RELATION TO THE NUMBER OF COMBUSTION CYCLES PER MINUTE
ONCE COOLANT BOILS it lost the full ability to absorb heat as partial direct contact with the metal surface is partially lost, one reason cooling systems are pressurized is to increase the boiling point threshold
http://www.newyorkrestomod.com/category_s/1820.htm
http://www.stewartcomponents.net/Mercha ... Code=Therm
viewtopic.php?f=57&t=149
viewtopic.php?f=57&t=853
viewtopic.php?f=54&t=2187
viewtopic.php?f=57&t=4701
if you have the room mounting the coolant temp sensor in the radiator t-stat housing location with a custom spacer for the sensors, is a good option as it tends to read more consistently than sensors mounted in the cylinder head.
http://www.summitracing.com/parts/MEZ-WN0028U/?rtype=10
http://www.summitracing.com/parts/MEZ-WN0028U/?rtype=7
Ive used those swivel t-stat housings several times, the seal o-rings generally seal, well and are easily replaced if damaged, the only issue I had was the t-stat housing is so tall it won,t fit in a few applications (clearances on some intakes like TPI)
theres two basic designs one uses an o-ring in a grooved base that seals against the manifold t-stat flange area , the o-ring is actually mounted to the center part of the neck that swivels has an extended outer round flange and the outer flange clamp part that bolts down applies pressure to the swivel neck seal and flange but never contacts the coolant fluids.
example
the second type requires a standard t-stat gasket
and the o-ring, the o-ring seals between the upper outer flange on the inner swivel neck, and the outer flange that seats over the o-ring seal that is held in place with the outer clamp ring that has the mounting bolts applying pressure
EXAMPLE
Corvette – Water Pumps
The "Corvette short" water pump which you refer to applies only to small blocks and not big blocks. ALL 65-74 Corvette big blocks use the same, BASIC water pump casting (although 4 different castings were used). All 65-70 big blocks use a bearing/shaft assembly with a 3/4" diameter shaft, but a PILOT (the end of the shaft which centers the pulleys and fan clutch) turned down to 5/8". 1971-74 big blocks use a full 3/4" pilot.
For Corvette small blocks, ALL 55-70 Corvettes use a "short" water pump with a 5/8" shaft. This same style water pump was also used on all 55-68 small blocks used in all other Chevrolet passenger cars with small blocks. In 1969, most Chevrolet small blocks and big blocks, EXCEPT CORVETTE, went to the "long" water pump which still used a 5/8" shaft. Block to hub face is 5-5/8 (5.625)
In 1971, virtually ALL of the small block water pumps changed. All, EXCEPT the CORVETTE, continued to be "long leg" style but with 3/4" shaft and 5/8" pilot. Corvette continued to use a "short leg" water pump, but it was a DIFFERENT short leg water pump than used for 55-70 Corvettes. This water pump, often referred to as the "Corvette short" water pump, was set up to accommodate the large bearing and shaft assembly which used a 3/4" shaft. For 71-82 Corvette pumps, the shaft PILOT was the full 3/4". The full 3/4" pilot small block water pumps are unique to Corvettes and some medium/heavy duty trucks which also used the "Corvette short" water pump. I might also add that 71-74 Corvette big blocks ALSO used the 3/4" pilot shaft and they were the only big block water pumps which did so.
Due to its design, the "Corvette short" water pump has a slightly greater block mounting surface-to-face of hub flange dimension. Block to hub face is 5-13/16 (5.900). Combined with the fact that the 71+ pump has the full 3/4" pilot, it is applicable to only 71+ model Corvettes (and the trucks mentioned). The "Corvette short" water pump is NOT applicable to 55-70 Corvettes unless the entire pulley system, fan clutch and fan are changed to the 71+ configuration.
I might also add here, for clarification, by water pump SHAFT diameter, I am talking about the portion of the shaft that goes THROUGH THE BEARING. All Corvette water pumps use a 5/8" impeller shaft end. For 65-70 small block Corvettes, this means that the shaft is 5/8" all the way from end-to-end. For 71+ Corvette small blocks, the impeller end of the shaft is turned down to 5/8".
There were several GM castings used for the 55-70 Corvette and 55-68 ALL small block "short" water pumps. However, for the 71-82 "Corvette short" water pump, there were only 2 castings ever used. 1971-early 1972 used GM #3991399. Later 1972 to 1982 used GM #330813. These are the only 2 castings which GM EVER used for the "Corvette short" water pump. The 3991399 has no drilled and tapped boss on the top for external bypass. The 330813 does have a large upper boss and 3/4" NPT fitting for external bypass. The external bypass provision was plugged with a square head pipe plug for all 72-82 Corvette applications. The fact that this boss and tapping was added to the pump was only for the truck applications that also used it.
Chevy Water Pump Specifications Summary:
Short-Style Pump for most 1955-72 cars & trucks (5/8" pilot shaft)
• Fits all 1955-68 S/B Chevy passenger cars, 1969-70 350 c.i.d. Corvettes and 1955-72 light duty trucks. Has 3/4" ball/ball bearing.
• Dimension from block surface to hub: 5-5/8". Inlet diameter: 1.80".
Long-Style Pump for 1969-87 V8, 90° V6 & 1973-86 truck (5/8" pilot shaft)
• Fits all 1969-87 S/B Chevy or 90° V6 passenger cars and 1973-86 light duty trucks. Does not fit Corvettes (use #8810 or #8812)
or late-model vehicles with serpentine accessory drive belts (use #8881). Has heavy-duty 3/4" ball/roller bearing.
• Dimension from block surface to hub: 6-15/16". Inlet diameter: 1.80".
Short-Style Pump for 1971-82 Corvettes 3/4" pilot shaft)
• Fits all 1971-82 S/B Corvettes. Comes with heavy-duty 3/4" ball/roller bearing.
• Dimension from block surface to hub: 5-13/16". Inlet diameter: 1.80".