Thermostat........Drill A Hole Or Not?
08-16-2015, 04:51 PM
#61
Melting Slicks
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An electric fuel pump is rated at the pump's outlet and the actual fuel delivery at the carburetor will be about half that due to frictional losses along the way. In my case my 100 gph Carter is delivering 55 gph at my carburetor and my engine consumes 53 gph at wide open throttle around 5500 rpm.
When the G.M. engineers designed the 82 thru 84 CrossFire Injection fuel systems they forgot to take into account frictional losses and assumed a 50 gph electric pump would be adequate. But at 11 psi the pumps only delivered around 36 to 37 gph which caused the engines to starve for fuel above 3500 rpm.
08-16-2015, 05:33 PM
#62
Melting Slicks
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Its not a myth and its absolutely true. You need to take a college course in thermodynamics to understand how an automotive cooling system works. I have and its a lot more complicated than you can ever imagine.
08-16-2015, 06:57 PM
#63
Well professor, next time proof read your lectures.
You started posting 100 GPM, then later changed it to 100 GPH. Rudimentary math tells me the difference is 5,900 gallons per hour.
You started posting 100 GPM, then later changed it to 100 GPH. Rudimentary math tells me the difference is 5,900 gallons per hour.
08-16-2015, 07:38 PM
#64
Drifting
But think about this:
In a closed loop, such as our cars, a given water molecule actually spends the same amount of time in the radiator, no matter how fast it is moving, as long as the water is indeed moving.
"Too much coolant flow is bad." This long-held radiator myth will not die. Too little coolant flow can be bad, but at normal and high operating temperatures, the rate at which coolant moves through the radiator does not change the amount of heat that is dissipated by the cooling cores. Sure, the mean temperature of the coolant will rise if it flows faster, but the amount of cooling will not be reduced.
This is a forum, I try to respect other's posts.
08-16-2015, 08:35 PM
#65
Drifting
A little more on coolant speed:
The flow rate of the coolant has no effect on a molecular level - the liquid is essentially an infinite reservoir, as there are always more molecules available. They will continue to absorb energy until the coolant in that region boils. The molecules are not shooting over the surface too fast to pick up heat due to a pump that is too big. However, lack of circulation could lead to stratification and local boiling.
What flow rate does effect is the temperature of the coolant in any given region of the system. Clearly too low a flow will allow a larger temperature gradient to exist from inside the heads to the radiator. You want that coolant circulating as fast as possible so that it moves the heat from the engine to the radiator as fast as possible. This will result in the greatest possible temperature difference between the coolant and the engine, and between the coolant and the radiator surfaces, which will give maximum efficiency of heat transfer.
The problem in implementation is that trying to circulate the coolant too fast results in other problems like cavitation and local pressure drops, so it doesn't work.
The reason why high flow pumps are not always helpful is not because the coolant is moving too fast to transfer heat, but because you can't just go jamming on a bigger pump and expect a system to get proportionately better – that's what engineering is for.
The flow rate of the coolant has no effect on a molecular level - the liquid is essentially an infinite reservoir, as there are always more molecules available. They will continue to absorb energy until the coolant in that region boils. The molecules are not shooting over the surface too fast to pick up heat due to a pump that is too big. However, lack of circulation could lead to stratification and local boiling.
What flow rate does effect is the temperature of the coolant in any given region of the system. Clearly too low a flow will allow a larger temperature gradient to exist from inside the heads to the radiator. You want that coolant circulating as fast as possible so that it moves the heat from the engine to the radiator as fast as possible. This will result in the greatest possible temperature difference between the coolant and the engine, and between the coolant and the radiator surfaces, which will give maximum efficiency of heat transfer.
The problem in implementation is that trying to circulate the coolant too fast results in other problems like cavitation and local pressure drops, so it doesn't work.
The reason why high flow pumps are not always helpful is not because the coolant is moving too fast to transfer heat, but because you can't just go jamming on a bigger pump and expect a system to get proportionately better – that's what engineering is for.
08-17-2015, 01:12 PM
#67
Drifting
I'm not sure if I wanna take your advice on this one. I work in a wonderful company in Silicon Valley. My job as a business analyst programmer is very creative, as well as very rewarding. I like cars, but don't really wanna sell them. I prefer to buy them... I hope this helps.
08-17-2015, 01:27 PM
#68
Le Mans Master
Jeff would be a horrible used car sales men as he didn't sell his car to me LOL.
He is better off as engineer. Now go fix your Bluecoat software.
BTW you guys are talking about dwell time and it can effect temps depending on radiator sizes and flow.
He is better off as engineer. Now go fix your Bluecoat software.
BTW you guys are talking about dwell time and it can effect temps depending on radiator sizes and flow.
Last edited by ddawson; 08-17-2015 at 01:29 PM.
08-17-2015, 04:34 PM
#69
Drifting
If a car runs a closed track at a constant speed for 1 hour, the dwell time at any given point is the same weather it travels at 10 mph or 100 mph.
The same is true of coolant in a radiator. If coolant speed is doubled; it spends half as much time in the radiator, but is there twice as many times. It ain't that hard...
The same is true of coolant in a radiator. If coolant speed is doubled; it spends half as much time in the radiator, but is there twice as many times. It ain't that hard...
08-17-2015, 09:53 PM
#71
I have never drilled holes in my thermostats and I have never had any problems. After reading many posts in Chevrolet forums about the "need" for a hole I decided to do it last winter just to see what difference it made. I drilled two 3/32" holes 180 degrees apart and reinstalled it. Well, right off the bat it needed a full 10 miles of driving before my heater began to work so I came to the conclusion the "need" for drilling a small hole or two is an urban myth.
First of all most intake manifolds are counter bored about 3/32" deep which is about 3 times the thickness of the thermostat flange. Which means coolant leaks around the edges of the thermostat anyway which also means a hole is just making the amount of leakage worse. And then coolant also leaks thru the center of the thermostat so what in the heck is the hole supposed to accomplish other than making the "hole driller" feel needed?
So what are the opinions of the forum "experts"? Drill a hole or not?
First of all most intake manifolds are counter bored about 3/32" deep which is about 3 times the thickness of the thermostat flange. Which means coolant leaks around the edges of the thermostat anyway which also means a hole is just making the amount of leakage worse. And then coolant also leaks thru the center of the thermostat so what in the heck is the hole supposed to accomplish other than making the "hole driller" feel needed?
So what are the opinions of the forum "experts"? Drill a hole or not?
Last edited by hdpete98; 08-17-2015 at 11:50 PM.
08-18-2015, 12:59 AM
#72
Race Director
I run a 1/16 hole in the lip where the stat closes, just keeps the fluid moving in the radiator. Helps bleed air out of the upper hose after a refill and does not affect the high flow balanced stat. I run 180 in both summer and winter with the a/c on or heat on. 
The mechanic I learned from 50+ years ago felt it took some shock out of the radiator by not getting the hot water in a sudden burst. Don't know if it's true, but my 1985 Camaro plastic radiator never failed - many others did ?
The new stats are very tight to get the engine warmed up fast to lower emissions, the old stats were somewhat sloppy and leaked internally. So I guess it's a personal preference...
The mechanic I learned from 50+ years ago felt it took some shock out of the radiator by not getting the hot water in a sudden burst. Don't know if it's true, but my 1985 Camaro plastic radiator never failed - many others did ?
The new stats are very tight to get the engine warmed up fast to lower emissions, the old stats were somewhat sloppy and leaked internally. So I guess it's a personal preference...