[GTO71]

I recently put my 400 back in my 71. I spent time getting the divider plate to about 0.10 away from cast impellar. Running a 4 core radiator with about 75/25 mix a antifreze to water with no theromstat. I run about 150 on a 75 degree day and now on the cool fall nights it is getting under 150. I was taught that this is really too cool beasuse the motor oil is designed to flow at a higher temp. Can these low temps be bad for me engine. Or is that justa myth, most boat engines run at this temp year round.

[Geoff]

Use a 160 degree high flow stat, as shown on the
www.stewartcomponents.com site, & your troubles are over.

[engineer]

below 150 is too cool to boil out an condensation products in your oil. a change of thermostat will not change operating temps. since running below the thermostat temp will not allow it to open properly.

[Malky]

engineer, you got me scratching my head - the t/s setting determines the MINIMUM engine operating temp, doesn't it? A change from no t/s to a 160 deg t/s will ensure the coolant runs at least 160 deg before it opens.

[GoatDr]

The thermostat only determines when the coolant flows from the engine to the radiator. The anti-freeze is circulated in the engine until the temp reaches a point at which the thermostat will begin to open. It is not possible to run at a temp below the thermostat rating. IF temp of fluid drops below that temp it will close and the temp will rise again and open.

[george kujanski]

He originally said he is running no thermostat.

I would suggest at least a 160 T-stat. As mentioned above the t-stat will maintain at least a 160 (approx) temp. If the rest of the system is working, the temp under other operating conditions will not be much above 160.

George

[DIYGuy]

I recall reading somewhere that higher temps (up to a point) can raise the engine's combustion efficiency, which (along with the benefit of smog reduction) is why the newer cars run at higher temps.

Not sure if this really applies to the older motors, and combustion chamber design has changed a lot since our babies were designed... so, mainly we are concerned about high temps causing detonation/knocking/pinging with today's crappy fuels.

Still, I think it is possible to run too cool, and lose some efficiency that way, including increased loss due to higher oil viscosity at the lower temps. Anyone out there know what kind of problems arise from lower operating temperatures?

[WCWhitey]

True about efficiency of the chamber at higher temps, but cooler under hood air also adds power. If he can put in a 160 and run at 160, do a happy dance and forget about it.

[DIYGuy]

Originally Posted by WCWhitey

True about efficiency of the chamber at higher temps, but cooler under hood air also adds power. If he can put in a 160 and run at 160, do a happy dance and forget about it.

Cool!

[68birdfreak]

I just had this conversation with my engine builder....Very interesting to say the least. This gentleman warrants his engines for a year! street or strip! He will blow you away with his pontiac knowledge. The scary sick motor he is building for my sled will love to hover around 200 degrees. I have been told 180 is perfect from every couch racer friend I have. Everyone has an opinion. He explained it to me and I didnt fully understand but did grasp the jist of it. Every engine is different, seek proffesional advice if you really want the answer and those may vary.

[TCSGTO]

My 455 runs best and ET's quicker at 190-200 degrees. It was the same with the iron heads before I put the E's on too. The AMC 390 in my AMX likes 160. I guess every car is different.

[Herb Hagan]

Originally Posted by engineer

below 150 is too cool to boil out an condensation products in your oil. a change of thermostat will not change operating temps. since running below the thermostat temp will not allow it to open properly.

Adding to what Engineer stated, water in your oil over a period of time will cause the oil to become acidic, which can cause internal damage.

Herb

[Greg Reid]

My Grandfather taught auto-mechanics in a trade school for nearly 30 years. When he died I inherited a lot of his text books.
One of the first books I read stated that not getting the oil up to a temperature that will vaporize water and fuel is detrimental to the engine. It gave the same reasons as stated earlier in this post by Herb Hagan and Engineer.
It even went as far as saying that it's a mistake to think that a car only driven short distances over a long period of time (eg., only to church on Sunday) benefitted from being pampered and that this type of driving, in fact, could cause damage to the engine.
BTW, this particular book was published circa 1965.

[Geoff]

Oil has been greatly improved since 1965.

[Greg Reid]

I'm sure it has but I don't think that it has improved to the point that it can eliminate contaminants from itself. An engine which was designed in the 1960s will produce water internally. Also, a certain amount of gas will contaminate the oil. Both of those contaminants will remain in the oil if not heated enough to vaporize. Once vaporized, they can be eliminated through the pcv circuit.

[WCWhitey]

Just as a note, most Pontiac engines used a 160 degree stat until emmissions became an issue. Also how often do we change our oil. I do mine at least twice a year and that adds up to about a 500 mile interval, the oil barely changes colors. LOL good topic. Bill

[Junkyard Dog]

160 is fine.

I used to run an engine without a thermostat for several years because it was hot in California and Arizona and New Mexico, where I did all my driving. I thought the water temperature gauge was broken, because the needle always rested on the left stop (as low as possible). I thought the engine must get hot, because the engine compartment had heat.

The oil always had this white milky stuff in it, so I changed it often, added STP, switched brands, did all kinds of stuff. The milky stuff was still there after several days of driving.

One day, one of my rotten old hoses let loose on a 110 degree day in the desert. The water temperature needle began climbing and was on the max by the time I stopped (what, it works?).

I changed out the hose, and the meter was back on the low point.

So, I put in a 160 thermostat, and the white, milky stuff disappeared forever.

I think now, looking back, that this was condensation.

The water temperature gauge worked fine! It stayed on 160, so I guess that car had a really good cooling system.