69 400 thermostat recomend
 

Going to flush out coolant and change thermo. Car runs around 180-190 in the summer. Never runs hotter. Problem is I replaced temp sending unit today and started car up and immediately watching radiater, coolant was flowing through it and it was a stone cold engine. Outside temp 70. seemed to run fine all summer unless it just stuck open today. Dont know how old anti freeze is so figured I would drain and fill. What thermo would be best 180?

If no issues, stick with what works for you. 180 would be fine. If you do any cold weather winter driving, then 195 so as to get some heat in the engine/heater. Keeping the engine cooler is good in helping prevent detonation IF you were having any. I like to run a 160, but that is me.

When you pull it out look on the bottom it will more than likely be marked what temp it is and get another one.

I live in a mostly hot climate. There`s tons of fuel boiling problems with today`s pump piss in carb`ed cars. I would run a 160 to keep the engine/carb as cool as possible.

I live in Florida and run a 195 year round in both cars now. Seems to run better with some heat in the engine. I do not have any problems with overheating/ vaporlock even with the AC on in stop/Go traffic. This is for my 78 T/A w/ a 462 auto, factory air and a 69 FB w/ a stock 400/ 5 speed vintage air car. 93 octane for the 462 and 87 for the 69. Champion Radiators, factory style clutch fan only on both. No electric fans....

There was a 180 in it but I installed a 160.

Can someone explain how installing a 160F thermostat allows the engine to "run cooler"? Given that normal engine operating temp is higher than 160F, how does installing a 160F t-stat actually allow the engine to run cooler? My understanding is that the only difference is that it will open sooner than say a 180F t-stat, but it has no impact on operating temp once the engine is warmed up. Am I missing something?

160 is what people have been telling me cause it runs cooler in hot weather. Carb running like crap so hard to tell if any difference.

I know some people say that, but I'm looking for a scientific explanation that supports those claims. I've seen many instances of people installing 160F t-stats hoping to cure overheating issues, and it virtually never makes a bit of difference.

Thermostat sets minimum operating temperature. If a cars entire cooling system is up-to-par, themostat temp is what the engine will run at. Engine that runs hotter than thermostat temp has something not working as good as it could.

Clay

Hmmm... Wouldn't an engine's minimum operating temp be determined by the heat generated by friction and combustion and only be mitigated by the radiator and t-stat? Knowing that a Pontiac V8 will have an operating temp of 180-210F with NO t-stat installed and all other cooling components functioning optimally, I don't see how using a t-stat that opens at 160F will change that.

Definitely not trying to be argumentative, just trying to learn something. :)

Like QuickSilver explained, it's really determined by how efficient the cooling system is. The thermostat just sets the minimum temp the engine will run, but you need to have a capable cooling system to see it.

If you run a 160 stat and the cooling system is subpar, then it will still heat up to a point where the cooling system can eventually maintain it, and that can be virtually any temp above the thermostat rating.

If you have a really good cooling system it'll maintain any low temp thermostat you put in there.


Removing the thermostat doesn't necessarily mean the engine will run cold, if the cooling system isn't that great to begin with.

I've just never seen a cooling system that is "good" enough to allow a Pontiac V8 to achieve an operating temp of 160F or lower with normal summertime outside temps.

Are there actually people here who have been able to achieve a 160F operating temp in summer driving?

Yep, we have a few cars that do it.

Our usual summer temps are well over 100 degrees here. So when it's that hot the cars generally run around 170-175 degrees.

Now that it's cooled off to the 80's the cars will run right at 163-165 degrees, which is where the thermostat is fully open.

Last weekend we drove up and over the mountain and the ambient temps were in the low 70's last Saturday. Mine was running 158 degrees right where the thermostat just cracks open, so it never gets any colder than that with the 160 stat. At times where I cruised with the rpm up for a bit I could get it to 163 degrees, but would drop right back down to 158-159 at low rpm and idle.

Dads car was doing virtually the same thing following behind me.

Huh, interesting. I'll have to see where I can get mine to run once it's all back together now that I have a new radiator, fan clutch, shroud, and water pump.