It's summer time here in NW Colorado. It was 91 degrees here I decided to see how hot the car would run driving around. My car is a 400 AC car with a stock 3 core raditor. If i drive normal it runs 200. If I drive it hard it reaches 210. This is with the AC off. Is this ok? The car has a 165 degree tempostat in it.

??? Is the car healthy...????

I would go to a 4-core and try to run it cooler. I have read that if you want to run 190 you need to be using a 190 thermostat, or 180 what ever temp you would prefer. How's you mixture of anti-freeze to water. Make sure it's at least 50/50 water is what takes you heat out of your engine. I lived in Vegas and was running my car with to much anti-freeze, I was over heating as soon as I changed to a 60 water 40 anti-freeze my car was running cooler. 210 is too hot, plus the air your pulling into your engine is not giving you the performance you could get if it was cooler under your hood.

I believe the water to anti-freeze is close to 50-50. I used distilled water...and the waterpump is new. Usually the temp runs in the 185 range. This is the hottest day of the year and I wanted to see what it would do. Plus I just put the AC back on the car. It was orginally an AC car with a 3 core...

When you changed your water pump were the sleeves installed? Also are all the shrouds and baffles installed? Things that people don't think of is your car properly timed?

What is the altitude that you are at in Cololado? That can cause you trouble. You may have to set your timming and carb. adjustment diffrent than stock to adjust to these conditions. I use to live in Denver and it is the mile high city.

When you run a colder than spec t-stat, it will initially open and then never close. You will have constant flow through the radiator, this equates to the coolant not having enough time to transfer the heat out of the system via the radiator. Put a stock temp thermostat in, should be 195 degrees, but check out what the parts house says. And make sure to have a 50/50 mix of coolant in the system. And no, 200 degrees is fine.

200 degrees is fine and normal for a 400 with A/C in hot weather with the A/C off. Mine does fine at that temp in gear in stopped traffic for hours during the Dream Cruise, the only complaining component was the trans as the trans fluid was not cooling sufficiently. If you don't typically sit idling in traffic for hours, you won't have an issue.

Some signs of an unhappy hot 400 are rougher and louder than normal sounding exhaust, possibly some stumbling, slow trans engagement (auto), burping coolant (you can smell the antifreeze even if it's not dripping) and loud ticking when you shut down.

After you've hit 210 and continue driving at normal speeds, how long does it take to drop back to 200?

The seems to adjust up and down pretty quick. When it hit 210 I was getting on it much more then usually and it took maybe 3 minutes to come down to between 200-205. I can see the temp raise if I nail it for say 30 seconds... But everything seems fine. The engine runs great. The timing is by ear (the car has a small cam). The carb could be adjust a little better probably a little rich I moved the car from 900 feet in Kentucky to 5400 here in NW Colorado. But I'm not sure it was adjust right in ky either...

I just wanted to check and see the consenus of the group of proper running temp. And is the 190 degree verses the 165 degree I have surprizes me.. I would think the 165 would help control the over all flow..

Thanks... Over the years this forum has been a wonderful resource...

As long as the temps come back down rapidly like that you do have sufficient cooling. I am surprised that you have a 3 row core, as most 400s only attain that efficiency with a four row core, unless it's a manual trans car and not burdened with that extra cooling load.

that temp is fine!
thats what mine runs most of the time here in Texas...195F 6,7 mo of the year...200 summer , with the eception of really hot days...its been running 210-220 in June ,early July...if you get over 225 I`d worry....but if you run it hard and slow down it can creep up for a short while...
mine is a 400 with automatic...and I drive "normally" 80-90...have a stock radiator.

This may clear up the three core. My car is a 400 4 speed car. But when i ran the PHS it came back as a 350 2 barrel auto car. So I see why it had the three core. I should of bought a 4 core when I purchased the three from Ames. I just didn't know at that time.

And I thought I was ok it's just the highest I have seen it and wanted to check. Wonderful!! Thanks

P.s. I have the Flex fan (stock) that doesn't have a cluch. Is this ok with AC? And anyone else have a [censored] of a time getting the compressor belt tight enough? It's hard to find a place to pry against to get the tention.

Flex fans are garbage. If you were to get the OEM 7-blade fan and clutch, you are likely to find that change by itself is going to make a big improvement.

Agree 100% on the 7 blade 19" clutch OEM fan. I had "hot" issues for my first 8 years with my car until the very day I bolted on the correct fan. From that day my car has NEVER run hot once. Now in addition to the correct fan I purchased ALL of the filler panels, rubber fillers, lower valance filler panel etc. but it was the fan that solved the problem for me...

Ok...does anyone have the OEM 7 blade fan with Clutch?? and if not where can I get one???? Thanks

I bought mine at a swap meet for $20. My Pontiac friend gets them from the junkyard almost every time we go. The came on MANY MANY GM models over the years and he gets them for $5.

We just look at all the cars and always find at least one. The last one found was off of a early 80s Camaro. Just be sure it's 7 blade and 19" from tip to tip and be sure the clutch spins free...

Then, be sure when you install the 7 blade fan that it fits inside the shroud as it should (half in, half out) when looking from the top or sides. I see them all to often either way inside or not even inside the shroud at all.

If you are lucky enough to find the correct length shaft, you will not need the spacer shaft. If you do need the spacer, you can get them from 1/2" thick all the way up to 5" long etc. You can always buy the 5" alluminum spacer and cut it down to the correct legnth for your application to ensure that your fan rests perfectly. Then you just have to find the appropriate length bolts...

well you just said it WAS a 350, now a 400...do you have all the fillers?
X fillers on top of radiator support, lower baffle...and rubberized filers on ea side of radiator bottom? those were on all AC and 400 cars, so if yours was a 350, these may be missing, if you install them it is probably a 15F+- less.

Used a GM 195* stat in my FB's for years.
Thats all Pontiac used from 66.
210 was normal. 220 sometimes.
This was with Stewart Warner gauges.

Flex fans are not garbage when used correctly.
Although i use factory 7 blade clutch on stock engines, my performance engines run cooler use'n flex.

I have a great local Junkyard to check with on the fan/clutch. And the advise on the placement is wonderful. The car does have the x fillers on the topbut, I don't think there is anything on side or the bottom. I installed the raditor and shroud is there anyone that has pictures for me of what a proper install looks like?