Thermostat Question
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Instructor
Joined: Aug 2007
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From: St. Louis MO
Thermostat Question
I have a 67 corvette with a 327/350 and I am replacing the thermostat. My original is marked 170 and I have the parts book for that year and it says it is a 170 degree thermostat. Since that doesn't seem to be made anymore, the choices are 160 degrees or 180 degrees. Every manufacturer seems to recommend the 180 instead of the 160. Any idea why? Keeping the cars cool as they get older would seem to be a typical problem so I would have guessed they would have suggested the 160 degree replacement? Just curious what the rational is?
Race Director
Joined: Apr 2005
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From: Bowling Green, Kentucky
Recommend that you install the 180 F thermostat. That is what most of us have in our cars.....especially if you live up north. I run it in my 327/350 HP car here in south Louisiana without issue.
The 180 F thermostat will help ensure that your oil temp is always high enough to boil off any condensation/moisture. That may not happen with the 160 F thermostat in cooler weather.
Larry
The 180 F thermostat will help ensure that your oil temp is always high enough to boil off any condensation/moisture. That may not happen with the 160 F thermostat in cooler weather.
Larry
Team Owner
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From: Washington Michigan
Le Mans Master
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From: Going too fast over the hill. Iowa
I got one for my 66
Race Director
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From: central FL, near the beach.
The thermostat has no effect on maximum engine operating temperature - it only serves to provide rapid warmup (to minimize internal wear) and controls the minimum temperature (as in winter, to ensure that the heater performs effectively). Maximum operating temperature is a function of the overall condition of the cooling system.
Melting Slicks
Joined: Sep 2003
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From: Orange Ct
The thermostat has no effect on maximum engine operating temperature - it only serves to provide rapid warmup (to minimize internal wear) and controls the minimum temperature (as in winter, to ensure that the heater performs effectively). Maximum operating temperature is a function of the overall condition of the cooling system.
Le Mans Master
Joined: Apr 2004
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From: Newark DE
Le Mans Master
Joined: Apr 2004
Posts: 7,106
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From: Newark DE
But wait, if the cooling system has more capacity than needed. The thermostat will close enough to maintain the temp thereby controlling the max temp. With enough cooling capacity, the temp will never rise much above the thermostat design temp. Keeping in mind that the stat starts to open at the design temp and becomes fully open at some higher value.
The MINIMUM operating temp is controlled by the t-stat since it stays close until the coolant in the engine block reaches the t-stat rated temp than it opens up therefore controlling the minimum operating temp.
After that the motor can operate at t-stat rated temp or higher - all based on the capacity of the system, not the t-stat.
Say the system has low cooling capacity because of radiator clogged with years of mineral deposits. The operating temp could easily go higher and higher until it overheats - the t-stat will do nothing to stop it or control it
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Le Mans Master
Joined: Nov 2000
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From: Going too fast over the hill. Iowa
johnz stated it correctly.
Also, if the cooling system has more than enough capacity to handle the engine and accessories such as A-C at all speeds and ambient air temps, then the engine temp should hover just above the tstat opening temp, which is what mine does.
Also, if the cooling system has more than enough capacity to handle the engine and accessories such as A-C at all speeds and ambient air temps, then the engine temp should hover just above the tstat opening temp, which is what mine does.
Last edited by magicv8; Aug 26, 2009 at 04:56 PM. Reason: spell
Drifting
Joined: Apr 2008
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From: Lexington Park Maryland
Having said that I have a 160 in my 327/350 because the day I bought it there were only 160s and 195s in the store. The popular 180 was sold out. I've had that 160 thermostat in my car ever since...... about 20 years now. I do drive in the winter but usually nice long rides so it's a moot point anyway as the motor runs long enough to get fully warmed up. Most of my driving is in the warmer weather anyway.
Instructor
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Safety Car
Joined: May 2003
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From: Ocean Township NJ
But wait, if the cooling system has more capacity than needed. The thermostat will close enough to maintain the temp thereby controlling the max temp. With enough cooling capacity, the temp will never rise much above the thermostat design temp. Keeping in mind that the stat starts to open at the design temp and becomes fully open at some higher value.
If you remove the rad support and replace it with one from a 1967 427, and use a radiator from a 1967 427 in your SBC, you STILL would not have enough cooling capacity to keep the coolant below about 190 degrees on a moderately hot day.
Don't believe me? Try this as an experiment. Remove the thermostat, and see if it makes any difference, at all, in your engine's coolant temp during the summer. Now, if you drive around without a thermostat in the winter (not recommended) then your engine's coolant WILL be too cold.
Le Mans Master
Joined: Mar 1999
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From: Itasca IL
John is, of course, correct. The thermostat only regulates MINIMUM engine operating temperature.
I would use a Robertshaw or Mr. Gasket 180 high perf. thermostat. Robertshaw P/N is 330-180 and Mr. Gasket is #4364.
On a side note, I was very disappointed that my recently acquired 67 427 would not run under 195 degrees while all my other Corvettes have run 180 without difficulty. It never occurred to me that the car had a 195 stat in it until I pulled the stat out for clearance to remove the temp sender. It's a 195. Had NAPA check their book when I was there yesterday buying some stuff for the Caddy, and sure enough 195 is what their guide lists as a replacement. No wonder!
I would use a Robertshaw or Mr. Gasket 180 high perf. thermostat. Robertshaw P/N is 330-180 and Mr. Gasket is #4364.
On a side note, I was very disappointed that my recently acquired 67 427 would not run under 195 degrees while all my other Corvettes have run 180 without difficulty. It never occurred to me that the car had a 195 stat in it until I pulled the stat out for clearance to remove the temp sender. It's a 195. Had NAPA check their book when I was there yesterday buying some stuff for the Caddy, and sure enough 195 is what their guide lists as a replacement. No wonder!
Le Mans Master
Joined: Nov 2000
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From: Going too fast over the hill. Iowa
I have heard that a factory style sb rad can do it too, but the owners I know with A-C cars use auxilliary electric pusher fans to assist with city rad cooling.
Melting Slicks
Joined: Sep 2003
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From: Orange Ct
true, but if the cooling system has enough capacity to keep the operating temps at the t-stat rated temp it's than the reason it's kept there is because of the COOLING SYSTEM CAPACITY.
The MINIMUM operating temp is controlled by the t-stat since it stays close until the coolant in the engine block reaches the t-stat rated temp than it opens up therefore controlling the minimum operating temp.
After that the motor can operate at t-stat rated temp or higher - all based on the capacity of the system, not the t-stat.
Say the system has low cooling capacity because of radiator clogged with years of mineral deposits. The operating temp could easily go higher and higher until it overheats - the t-stat will do nothing to stop it or control it
The MINIMUM operating temp is controlled by the t-stat since it stays close until the coolant in the engine block reaches the t-stat rated temp than it opens up therefore controlling the minimum operating temp.
After that the motor can operate at t-stat rated temp or higher - all based on the capacity of the system, not the t-stat.
Say the system has low cooling capacity because of radiator clogged with years of mineral deposits. The operating temp could easily go higher and higher until it overheats - the t-stat will do nothing to stop it or control it
Race Director
Joined: Oct 2000
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From: central FL, near the beach.
t-stat controls the minimum maximum.
.
the OP asked a GREAT question imo. paraphrased "Does an old car last longer if it runs cooler"
That is debatable of course.
I say, quite the opposite; it wears faster if it runs cooler. It is easy to make it run say, 195F and make it last longer, but that is counter-intituitive to many, i suspect.
.
the OP asked a GREAT question imo. paraphrased "Does an old car last longer if it runs cooler"
That is debatable of course.
I say, quite the opposite; it wears faster if it runs cooler. It is easy to make it run say, 195F and make it last longer, but that is counter-intituitive to many, i suspect.
Last edited by Matt Gruber; Aug 27, 2009 at 06:37 AM.
Le Mans Master
Joined: Apr 2004
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From: Newark DE
The radiator does NOT have the capacity to keep the engine at 160, 170, or even 180 degrees in anything more than, say, 70 degrees ambient. Newer cars have much more capacity, older cars do not. Especially C2s because or limited space.
If you remove the rad support and replace it with one from a 1967 427, and use a radiator from a 1967 427 in your SBC, you STILL would not have enough cooling capacity to keep the coolant below about 190 degrees on a moderately hot day.
Don't believe me? Try this as an experiment. Remove the thermostat, and see if it makes any difference, at all, in your engine's coolant temp during the summer. Now, if you drive around without a thermostat in the winter (not recommended) then your engine's coolant WILL be too cold.
If you remove the rad support and replace it with one from a 1967 427, and use a radiator from a 1967 427 in your SBC, you STILL would not have enough cooling capacity to keep the coolant below about 190 degrees on a moderately hot day.
Don't believe me? Try this as an experiment. Remove the thermostat, and see if it makes any difference, at all, in your engine's coolant temp during the summer. Now, if you drive around without a thermostat in the winter (not recommended) then your engine's coolant WILL be too cold.
Even on very hot days around here (in the 90's) mine stays right at 180-185º no matter city/traffic or highway.
In fact it was right about 90º or a little more yesterday and fairly humid making it a pretty uncomfortable day. I had meeting about an hour away from me up in King of Prussia, Pa so I drove the '65. no matter if I was in traffic or I was doing extended fast cruising (about 75-90mph on the higway) my temp never went above 185.
I have Dewitts rad in my car that is approx 12 years old and it keeps the temps down just fine.
