[tjs72lemans]

I wanted to post this and found another post similar, but didn't want to hack his thread.
New build 400 bored .03 over. Mostly '72 stock low compression (8.0). Dynoed and now about 30 miles on build. Has a clearanced water pump and 180 thermostat and 1/8" hole drilled in base flange with 50/50 anti freeze. Has AC and new stock style Hayden clutch fan with shroud. Has new Cold Case radiator. Automatic.
Runs normally at 190 degrees even on hot humid days. At light in town goes to 195 and back down when moving.
Issue I see is, on 95 day and wanting to put load on engine going up steep, winding hill about a mile long in second gear, car with AC on got up to 210. Shut AC off and at top of hill turned around and head back down. Cools down to 195. Next day back up hill with AC off. Back up to 210-215. Cools back down on way down hill and hiway.
Is this normal? It gets to approaching 220 which makes me uncomfortable and wonder where it could go.

[ZeGermanHam]

If you're at 210F while moving, I'd say that's a bit too warm to accept as normal even if traveling up a hill. How much space is there between your radiator and your A/C condensor? What's your ignition timing? Also, with only 30 miles on the engine, it's hundreds of miles from being broken in depending on who you ask. Perhaps that is a contributing factor as well.

[PunchT37]

Put some more miles on it. New builds tend to run hot for a while. As they wear in, these heat problems often settle down to normal.

[steve25]

What do you have for a carb on the motor?

How many rpm was the motor turning in 2nd gear going up the hill?

It would also be nice to know the vacuum level the motor was pulling going up the hill.

[389]

First thing I would do is get a Stant SuperStat 160 degree. Make sure its a Stant there the only ones making decent thermostats today. Drill a very small hole in the base of the thermostat.. Just one little hole will do. Fill the engine up with one gallon of green antifreeze and the rest water. If your tap water is bad, use distilled from the super market or water from your dehumidifier...

If that doesn't do it, check and see where the clutch is set at on the fan they can be adjusted. That little coil can be moved to slip less and make the fan faster longer or slip more which would take less power to run but the fan would go slower.. Its like a little torque converter inside one of those things.. They are the best way to go, fully engaged they can move 7500 to 8500 CFM at 1500 rpm. That's no typo.. The electric fans are really silly little toys when put up next to the big clutch fan on a v-8 engine.. They also offer continuous air movement which is how the engineers designed these cars to operate. Not only for engine operation but for interior comfort. The AC will be working extra hard moving the additional heat out of the cab with the electric fans slowly pumping a small portion of the additional heat right into the radiator..

Next time you have the hood open on a car with a clutch fan feel how strong the air is blowing..

[geeteeohguy]

Put more miles on it. Normal for the temps to rise going up a grade under load on a hot day. As long as it doesn't overheat/puke out coolant you are okay. Break in the engine and get back to us.

[Formulas]

Such a long list of things to make our Pontiacs run hotter than need be

It can be broken down to 2 basic sections producing to much heat or not shedding it well enough

Sounds like you have put a fair amount of effort into shedding I would look at spark curve and Jetting original stock isnt going to be perfect with todays gas and a rebuild suggests newer camshaft a little more compression all of which changes things and 1972's were jetted clean to start with even leaner with today's gas

[tjs72lemans]

The condensor is in stock location from radiator in support (one inch clearance?).
Timing at dyno session at initial at 12 degrees. After market HEI, advance not checked.
Stock carb rebuilt/tuned by Cliff. Running rpm up and down from 2000-3000.
The stock fan definately moves the air.
It never puked, just seemed warmer than I was expecting. I figured it may be tight and running warmer, but does a good job with temps in the 90's through town.
I figured this 30 degree angle hill to top of bluff would be good for some break in runs up and down. But, found it doesn't like that right now.

[i82much]

i think you need to drive the car a lot more before you start worrying. 30 miles isn’t much. mine has 2500 miles on it and seems to run noticeably better than it did 1500 miles ago.

[tjs72lemans]

Took the car for a ride down the hi-way and through small towns on the hi-way. Destination was about 65 miles. I have about 200 miles on rebuild.
Car runs at 195 in town and on hi-way (even at speeds of 70 mph). But, on hi-way at 60, as more power is needed on long gradual hills, temp runs up to 205. Once at destination, ate and came back to car and noticed a small wet spot on ground (about 2 sq. ft.). So, after shut down, the absorbed heat sitting must've caused enough pressure to pop the relief on the radiator cap. My manual gauge read 220 when I jumped in car. Fired it up and it quickly came down to about 205 and further as it ran parked. The temp outside was actually cooler (about 80) compared to previous runs. The radiator never spit out before.
Is it possible I actually need a higher pressure cap? Can a running 195 temp shut down and reaching 220 cause this?

[Formulas]

Could be to lean during those long gradual hills power circuit to slow to kick in...
Can also be timing related.
Cooling system could be the symptoms not the cause

Timing is easy to figure out fuel mixture is harder need an O2 gauge or trial and error with some plug reading

[Goatracer1]

Could be radiator was just too full.

[dataway]

This won't be the solution to your problem, but something you should check anyway. Make sure the frame horn seals are there, make sure the lower seal between the bottom of the radiator and the core support is there and that there are no large gaps around the edge of the radiator and the core support. At road speed these help make sure air is going through the radiator, not around it. AC cars need these seals in place.

[lust4speed]

For testing - take the thermostat out. Regardless of Chevy wife's tales a Pontiac with no thermostat will run as cool as a perfectly working thermostat. If your thermostat is like 95% of those I test on the stove it could be most of your problem.

Next, a 50-50 mix of antifreeze is definitely not the best solution for heat transfer. Pure water (distilled preferred) has the best transfer and the rate deteriorates as anti-freeze is added. One bottle of Water Wetter has more rust and corrosion inhibitors in it as a gallon of anti-freeze and it really does help cooling. Raising the boiling point higher with anti-freeze doesn't do any good if you have an equal rise in running temperature.

No way really to test a clutch fan, but it might not be engaging as tight as it should. When you hit 210-215 a good clutch fan will sound like a helicopter landing on your roof.

Most aftermarket HEI units (especially the ones Skip White sold) have between 20-22 degrees of advance. If you are setting it at 10° advance you probably only have 30° total and with a slow advance curve you timing could be too retarded and adding to the heat problem.

New engines do run warm and the problem decreases as you accumulate miles.

[steve25]

Fact!
Above 30 mph no car needs a operating fan any more if the cooling system has enough capacity for the rpm the motor is at and if the Jetting and timing are correct for the hp being produced at that rpm.

I have had clutch fans that where not freewheeling at road speed which was then blocking added air flow from moving thru my rad and of course making the motor run hot.

If you do not have vacuum advance working in part throttle situations then that in tself can make for higher temps being seen.

Gez, I mean just look at most 1/4 mile race cars running in down in the 10s with a electric water pump and electric fan, there staged at 140 to 160 degrees and only at the top of the 1/4 or slowing down does the fan kick on.

That should tell you something I would think!

[Half-Inch Stud]

High Head temp may have air pocket.
Check coolant level to be at top, after car cooled-down (on a slight incline is fine).
Surely the overflow hose is connected and tight.

[Gary H]

Have you checked the temperature with a temperature gun to see if your gauges are correct? I would do that first.

[67Fbird]

or boiling water and check YOUR actual sender and gauge....on the car. Seems every sender sucks....some more than others. BTW don't forget to ground out the sender when it's in the pot of water....and KEY ON!

[grivera]

Originally Posted by lust4speed

Next, a 50-50 mix of antifreeze is definitely not the best solution for heat transfer. Pure water (distilled preferred) has the best transfer and the rate deteriorates as anti-freeze is added. One bottle of Water Wetter has more rust and corrosion inhibitors in it as a gallon of anti-freeze and it really does help cooling. Raising the boiling point higher with anti-freeze doesn't do any good if you have an equal rise in running temperature.

In Minnesota OP needs anti-freeze

[tjs72lemans]

I wondered if the timing could be an issue with long slow uphill climbs. I do have the TCS disconnected.
The radiator is filled about an inch below top. I didn't notice any spit out in the past few runs after shut down. I would've noticed that in the garage for sure. But, it may be still trying to find that sweet spot in the level.
I do not have the frame horn seals. I do have the lower radiator core support air dam though.
I'm not sure what my total advance is. I do know it was set on the dyno with 12 initial.
I really need to check and make sure my vac advance is functioning. It's a new cheap HEI, but seems to work well otherwise.
Overflow hose is connected and tight. I've checked the coolant level a few times in the last runs and it seems to be close to an inch below top. That's about where I filled it with 50/50 anti freeze premix when engine was installed.
This sender/gauge from Bosch is mechanical, so I can only assume these are calibrated and tested to read correctly since the line and gauge stay connected at assembly. My temp gun does read about the same.
During rebuild, I initially bought a 160 thermostat and switched it to a 180 due to the talk on this site about running too cool. Maybe with it running hotter than the 180 thermostat, I should consider going to a 160.