[Darth Menace]

Hey, I'm replacing the upper rad hose soon and thought I had might as well change the thermostat too. What temp thermostat works best for the 400ci motor?

[67drake]

I run a 160 degree.

[67GTONUT]

I run a 180deg with (2) 1/8" holes drilled in the flange.....

[David Jones]

I think a 180 is the most popular. I run a 180 degree Stant Superstat that I drilled 3, 1/8" holes in for ease of filling purposes.

[rexs73gto]

I run the 165 stant super stat with no holes drilled in it & it works best for me. The cooler the better.

[Darth Menace]

Originally Posted by rexs73gto

I run the 165 stant super stat with no holes drilled in it & it works best for me. The cooler the better.

I heave read about people drilling holes but have no idea what they mean. what's the purpose of this and where do we drill these holes?

[Kenth]

Factory replacement´s are 195°F.

My GTO´s got them, no problems in at least 20+ years.

I guess the engineers knew what they´re doing?

A too cool running engine wears and got less economy/efficiency.

[straycat]

180 with the holes, forever. Never over heated in any type weather or traffic. Did the holes make a difference or is it the radiator, fan, pulley combo in the 455 that's in my 68, I don't know.

[David Jones]

Cool operation is more a product of having the correct tune.....mixture, timing etc than what temp thermostat you run. Have the tune wrong and you could ditch the thermostat and still not keep it cool....or get it up to temp. I've run 160's, 180's and 195's and they all work as designed. Running a 160 was somewhat scary.....pop the hood and it seemed to cool. Placement of the fan correctly in the shroud pays dividends in cooling. The right fan is important. The right fan clutch. Get the details right and you'll be golden........
The holes in the thermostat allow the coolant to more completely fill the system during a coolant change.

[JVM225]

I run a 195 with no problems. If the car runs hot with a 195, then something else in the cooling system is causing it and needs to be addressed.

[Darth Menace]

I know I ask this in every thread, but is there a proper ft/lb to torque the thermostat housing to, or is this another case of just tighten it? I assume it's the first option considering all the pressure it's under

[Greg Reid]

About 30 lbs will do it. Myself, I 'just tighten it'.

[David Jones]

Originally Posted by Greg Reid

About 30 lbs will do it. Myself, I 'just tighten it'.

My method too Greg. Make sure all surfaces are clean, flat and I put a VERY light smear of red sealant on the gasket.

[rexs73gto]

According to Pontiac the T-stat bolts should be tightened to 24 lbs. Also the holes in the T-stat are there for better circulation when cold & also helps when it it gets hot to help keep the steam in the system to a min. by letting more water go through the T-stat to help in circulation. Yes it is better to have a hotter running engine for better miliage but for power you want a cooler running engine. I'll give up a mile or to for a stronger engine.

[muscle_collector]

I would say a few factors would play into it.
what part of the country are you in?
what do you use the car for? (daily driver, short trips, cruising etc..)
how long of drives do you do?
here in Oklahoma using a 160 is perfect in the summer time. in the cold part of the winter the car will never warm up. on my car that I built to cruise town, since it is such an easy change, I used to switch from a 160 in the spring summer fall to a 180 in the winter.

[rexs73gto]

When I was younger & drove my cars almost all year round I would use a 185 stat in it as I wanted some warmth to, but now I don't drive any of the toys in any bad weather I keep the 160 in them all the time. The only driving I get to do with them now is in town & some travel to shows but don't take it say on trips as I afraid it will get stolen if I park it where I can't see it now. I would love to be able to take my 73 GTO on a vacation trip becasue it drives so good but I think it would go away if I parked it somewhere for any lengeth of time.

[Darth Menace]

I put on the thermostat/housing and went to put on the upper rad hose and this is what I saw. Both hoses are the same length but the one I bought today has a 90 degree bend where it goes into the thermostat housing. What did I order wrong? I ordered an upper rad hose for a 70 GTO but it was obviously a bit wrong. My wife say she can solve the problem with a hair dryer, but that doesn't sound convincing.

[David Jones]

Have you tried them?

[salem1912]

Originally Posted by Darth Menace

I heave read about people drilling holes but have no idea what they mean. what's the purpose of this and where do we drill these holes?

You are drilling a bleed hole or holes to help bleed trapped air pockets from the system.it helps with the first time you fill the radiator get air out that gets trapped behind the thermostat. Also if the car sits from long times. All new cars have this and it's so small a hole it won't add or subtract from the cooling process. In this picture you see the little valve this is the bleed. You don't need the valve just drill a 1/8 in hole.

To the OP I use a 180* no problems.

[salem1912]

Originally Posted by David Jones

Have you tried them?

X2- I think it's suppose to have the bend.