What Is Correct Factory Thermostat Temp for '73 350

FS87LT

Member
Apr 3, 2010
45
DFW, TX
Seems like the 195 F thermostats go back to about 1969 as OEM factory equipment. Yes, related to emissions control and keeping the engine hotter means fewer HC out the tail pipe. Prior to that, 180 was the accepted OEM factory equipment thermostat on the vast majority of USA engines (other than some middle-1950 Buick V-8s, which spec'd 160 F thermostats . . . they had cooling issues even with that low temp thermostat).

Keeping the engine hotter makes for a cleaner internal engine, meaning less condensate/oil issues, which can result in a milky top of the dipstick, by observation. EVEN with a fully-functioning pcv system. It takes engine motor oil longer to get to "operating temp" than engine coolant, which means short trips are bad and the oil needs to be changed more often in those situations. Usually about 10 miles of run time, even in 70 degree F weather.

In the later 1960s, 195 degree thermostats and AIR pumps were perceived to be "saps" on engine performance, mainly due to the hotter underhood air temps going into the carb (which generated lots of "cold air induction" systems by the OEMs and aftermarket people. Although the higher temps mean hotter air going into the air cleaner/carb, so ultimately better fuel atomization results. Consider, too, that as soon as the fuel is atomized into that underhood-temp air, the charge gets a bunch cooler, as a result.

On my '77 LT V-8, with the OEM 195 thermostat, the needle stays at 12Noon when at operating temp. With a 180 thermostat, it goes down to about 10AM position. Just the optics of that make me feel good and know everything iw working well. With both a 3-core Modine or the ACDelco "Upgrade" radiator (an '87 ElCamino OEM composite radiator). I really do like the way the composite radiator cools things!

As for those "HP" motors using a cooler thermostat? Remember they usually had 11.0:1 CR, which can work better (fuel octane and spark advance) with 180 thermostats, I suspect. Kind of similar to the Caprice LT1 engines being reverse flow, to cool the combustion chamber first rather than cooling the cylinders first. Which dirt trackers had been doing for years prior to that and Moroso sold a kit to do the conversion.

From my experiences, a 180 degree F thermostat, a FACTORY housing water pump, factory fan clutch and fan, fan shroud, and a CLEAN-internally 3-core copper or (later) composite radiator should keep a small block Camaro cool and long-lived. No need for fancy chemicals, different pulley drive ratios, or high-flow pumps, from what I've seen over the years. Also make sure the water passages in the BLOCK are free of age-related-accumulations, too!

My observations and experiences,
FS87LT
 

Newine

Member
Mar 7, 2014
32
Seymour, Ct.
What is the correct (stock) operating temp thermostat for a 73 Camaro w/350 (AC)? I have been using a 160 degree and was recently informed this is "too cold" for my engine / casual cruising operation. I always thought colder is less wear and tear on the engine, but apparently not the case.

Looks like 195 is where I need to be. Thanks for the help.
We used to put a 160 in for the summer( opens sooner, circulates water), and 195 in the winter( stays closed longer, builds heat for cold Conn. mornings).
 

joseph lamb

Member
Jan 1, 2017
68
tampa florida
What is the correct (stock) operating temp thermostat for a 73 Camaro w/350 (AC)? I have been using a 160 degree and was recently informed this is "too cold" for my engine / casual cruising operation. I always thought colder is less wear and tear on the engine, but apparently not the case.

Looks like 195 is where I need to be. Thanks for the help.
I have owned my 1973 RS for over forty years in Florida and would never run less than a 180 degree thermostat here . I guess i would ask if you have areally good after market temperature gauge on your Camaro ??? I have used a PRO Comp gauge since 1997 and it is really accurate for me . I have a L82 350 and auto trans and 3.73 gear and original fan set up . This 350 has always run at 180 degrees .....unless I get stuck in rush hour traffic , then it will climb up pretty quick which invites vapor lock on a stock intake . Yes, the hotter you can run is better , and moisture in the oil will result from the wrong thermostat or taking alot of short trips . Good day !
 

sandlapper

Veteran Member
Oct 9, 2020
1,188
SE CSA
If you have persistant overheating on any old motor, much of that can be due to the block/heads/rad being very dirty with scale and/or sediment. That means they ALL need a good cleaning ... not simply a flush ... but a serious chemical cleaning. The wimpy-azz citrus flush on today's shelves won't CUT thru heavy scale/sediment. Do a search for cleaning procedure using Oxalic Acid (DAP wood bleach crystals) followed by neutralization and lots of water flush. The old & discontinued Prestone Heavy Duty Cooling System Cleaner was a two part canister (way before Pringles) with Oxalic acid / neutralizer; DuPont had the very same thing. GM carried it under a GM pn. No More! Do it w/ wood bleach. Google it ... there was even IS a GM TSB on it (see below) w/ a good procedure from about 1999-2000 (when the good stuff was still available).

FWIW, Arm & Hammer Super Washing Soda is Sodium Carbonate (Not Bi-carbonate) and is the same Neutralizer as in the aforementioned HD cleaners. Google ... Google.

The GM TSB is # 99-06-02-12D
Get a free DexCool plugged radiator service bulletin (#99-06-02-012D) printout at GM dealer Svc Dept ... it'll walk you through a cleaning procedure that REALLY works. BTW ... proper procedure w/ AS100 takes about 4 hours at high-idle. Use the GM procedure/TSB as a guideline ... do it right and this stuff REALLY WORKS WELL.

The old Prestone AS100 Canister contained:
9 dry oz of Oxalic Acid (DAP Wood Bleach)
2 dry oz of Sodium Carbonate (Arm & Hammer Super Washing Soda)
--------------------------------------------------------------------------------------------------


thanks to Noonie & J

I sandlapper have also done this very procedure several times and always had very good results. I highly recommend. The only way you'll get em any cleaner is to remove them and have shop either bake & blast or hot tank the block & heads plus rad shop acid cleans rad. YOU must wear eye protection & rubber gloves... told ya!
 
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pooch400

New Member
Feb 21, 2012
18
waterbury
Water still boils off at 212 degrees. A 195 thrrmostat keeps the moisture out of an engine.
Water does boil at 212 degrees, but every pound of pressure raises the boil point 3 degrees. A 195 degree thermostat doesn’t keep moisture out of an engine any more the a 160 degree thermostat. A cooler thermostat won’t cause any damage. I hope this helps clear up any confusion. I’d be happy to elaborate if there’s any confusion.
 

wnmech

Veteran Member
Jul 20, 2014
1,414
grand prairie tx.
My boat with a 1999 Chevy 350 engine on the lake won’t ever get above 175 degrees. Heck I don’t even know if there a thermostat in the darn thing since I’ve only owned it for around 4-5 months
 

cadillac_al

Veteran Member
Apr 22, 2015
1,069
Maine
I'm sure there a
Water does boil at 212 degrees, but every pound of pressure raises the boil point 3 degrees. A 195 degree thermostat doesn’t keep moisture out of an engine any more the a 160 degree thermostat. A cooler thermostat won’t cause any damage. I hope this helps clear up any confusion. I’d be happy to elaborate if there’s any confusion.
I'm sure there are plenty of people that don't care about water condensation in their engines. It doesn't matter to me if they are confused or not. Race cars may have thiier reasons for running cooler thermostats but there is no reason to on a street car. GM already figured that out over 50 years ago.
 

pooch400

New Member
Feb 21, 2012
18
waterbury
I'm sure there a

I'm sure there are plenty of people that don't care about water condensation in their engines. It doesn't matter to me if they are confused or not. Race cars may have thiier reasons for running cooler thermostats but there is no reason to on a street car. GM already figured that out over 50 years ago.
You are incorrect about condensation in an engine with a 160 degree thermostat. The engine gets hotter than the thermostat rating. If you were to put a pot of water on the stove and bring the water temperature up to 160-180 degrees it would start to create steam. Therefore any condensation that formed in a cold engine would evaporate after the engine was run at operating temperature long enough to get the oil up to temperature. You are also incorrect about no reason to run a cooler thermostat on a street car because GM figured it out 50 years ago. Most things on a production vehicle are a comprise between government regulations, being flexible enough to run in a variety of different climates, and production costs. For example replacing factory manifolds with headers and a free flowing exhaust makes a difference on a street car. I don’t want to sound condescending, but there is a lot of confusion in the hot rod and the automotive industry because of opinions. I only want to educate and not put anyone down because I care. Like Joe Friday said, “Just the facts.”
 

pooch400

New Member
Feb 21, 2012
18
waterbury
Originally the thermostat would have been 180 degrees. 195s we’re not as common until computer controls.
Originally the thermostat would have been 180 degrees. 195s we’re not as common until computer controls.
In 1969, 195 degree thermostats were used on everything except high compression engines to elevate combustion temperatures in order to reduce unburnt hydrocarbons. The higher combustion temperatures also helped to ignite the leaner fuel mixtures that followed. The issue then became NOx emissions because of the elevated combustion temperatures. The EGR came out in 1972 for California and 1973 for everyone else. Then catalytic converters in 1974 for California and 1975 everywhere else. The only good thing that happened in the 70’s was the HEI distributor.
 




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