Recently finished a complete resto on my 79 ***  On the way to my first show she decided to overheat waiting to get into the show.  Idling it does not like and hits 220 and continues to rise.  I immediately assumed the thermostat was the problem and replaced with a new 195 degree with bypass.  I tested the stat in a pot of water and it opened at 200 degrees.  Install and same problem.  In fact the radiator was cold as well as the upper hose.  I even tried it without a stat to ensure the "NEW" pump was circulating properly.  It was so I refilled with coolant just below the thermostat then installed the thermostat and tried again.  Same thing - 220 and climbing.  

ARGGGHH...even if my timing had some impact it should still circulate through the radiator.  Going lower on the stat isn't necessarily a solution either....

Any thoughts or experiences anyone!

Jim  

I have a 400 in my 78 TA (see story I wrote in this forum).  If your radiator is not getting hot, that would indicate to me the liquid is not running through the radiator.  I had the same problem and if you do not know, all those 400s are known for overheating in the first place.  OK, if you already tried to flush the radiator to clean it, then you may need to replace the radiator and or try the following made by Redline, available at race shops.  WaterWetter® is a unique wetting agent for cooling systems which reduces coolant temperatures by as much as 30ºF. This liquid product can be used to provide rust and corrosion protection in plain water for racing engines, which provides much better heat transfer properties than glycol-based antifreeze. Or it can be added to new or used antifreeze to improve the heat transfer of ethylene and propylene glycol systems. Designed for modern aluminum, cast iron, copper, brass and bronze systems. Compatible with all antifreezes, including the latest long-life variations.  My problem, like yours was solved, pretty neat to ride around with approximately just under 200 degrees even in the hottest weather.  So now I use it in all my vehicles, hence cooler engine, better performance.  

Thanks for the tip Dave,

I installed yet another thermostat and success!  However cooler is better so I'm going to research where to get the product you mentioned.  The 4 core radiator was just cleaned at the local radiator shop which I failed to mention.

Have you ever used a phenolic spacer under your carb?  I tend to get what acts like vapor lock after its been up to operating temp and I try to restart.  

The effects of distributor timing can mimic a thermostat failure, and cause the same result, a rapid overheating of your Pontiac. Double check that your timing is 7-degree to 9-degrees BTDC and not any different. Also check your harmonic balancer for your true TDC mark, it is possible you are reading your timing wrong.  

It was a long time ago, around 1992, but I took a my carberator gasket and had a machine shop trace it and make an aluminum spacer for me, if I recall correctly and I could be wrong, it was somewhere between 1/4 to 1/2 inch high.  I remember I had to be careful to make sure the shaker would not go too high.  

My newly rebuilt 400 was running hotter than I like (220-240)and I found that by following the proper proceedure of getting all of the air out of the cooling system, installing a 160degree 'stat, and an overflow bottle I got it to run 210-220 degrees consistently.  Not as cool as I want, but a lot closer.

To get the air out, remove the radiator cap when engine is off and cold, make sure the radiator is fully filled with fluid, start the engine with cap off and let it run to operating temp.  As it warms up, keep topping off the radiator with fluid. You will probobly notice air bubbles surfacing as air is being forced from the relatively high pressure of the cooling system out into the air.  Let it run until you can no longer add any more fluid.  I was surprised that mine took well over a gallon more fluid during this proceedure.  This will insure that the complete system is full of fluid and it purges the air out as the fluid is circulating through the system.  

Well I have the engine overheating issue under control 200-210, but now after running the engine at operating temp and turning it off.  The starter labors something aweful and I have to let it cool way down before it works again.  Its so bad it won't start the motor it turns so slowly.  It acts like the battery is almost dead.  The battery is fully charged in fact its only 1 month old.  I even made a heat shield for it but that proved to not help at all.  Is it possible the starter has expired to the extent that it will only crank efficiently when the motor is cold?  Maybe the solenoid is the culprit.  This car needs to restart even when its warm or I can't take it anywhere of any distance.

You have to love these cars in order to not get completely frustrated with them.  

Had the same problem with a new rebuilt 400 it would start and run fine after only afew minutes of running and getting up to temperature it wouldnt start it would try to turn over but wouldnt. Let it cool down and it would start right up found it to have the wrong starter and it wasnt big enough it was for a newer V6 engine changed the starter and it works good  

Here's another tip to try, it concerns the space between the water pump impeller and the divider plate on Pontiac V8's. http://www.wallaceracing.com/water-pump-mods.php.
Haven't ried it, but it might help.
Steve  

Barneyformula is on the right track!!!
It happened to me for almost 5 yrs of over-heating and it was so simple to fix,,if you know what to look for. On all Pontiac v8's from the 70's there is a plate in between the water pump and the housing that forces the water to flow in one direction,,,without it your car will run but the antifreeze won't circulate through your radiator to get cooled. Look at your water pump from the top,,you should see the water pump, a gasket,then a piece of metal(which is the divider plate)then another gasket.If you only see the water pump and a gasket,,,your problem is solved!!!! YOU NEED TO GET THE DIVIDER PLATE and put it in between your water pump and engine block. I had no idea that my motor never had one!! Then i went to the junkyard and found a Pontiac 350 and took it apart and found the plate that my motor was missing!!! And now to fix your stater problem (I had that one too!) Ford had 1 good idea,,, a separate selenoid form the stater...they sell them in performance magazines,,,just get it and install it on your fender well somewhere..it bypasses your exsisting selenoid (which is to close to the exhaust and gets cooked!) and VALLA!  problems solved!!!NO MORE OVERHEATING AND NO MORE STARTER FAILURES!!! I put one in my car 12 years ago and wished i had done it sooner!!! It is the only good idea Ford had. Trust me,,,,my car was so hot,,it was boiling the anti-freeze and melted my overflow tank!!! Hope this helps you!!!  

I have a 71 Formula 400 with overheating issues. I tried the idea of removing the radiator cap and starting the car to remove air pockets. When I shut the car off the radiator spit maybe a half gallon of radiator fluid. What would cause this? Could it be the divider plate as mentioned in a recent reply? I have had this car restored and have had the heads redone and added a Lunati mild cam with a edlebrock intake and a holley 650 carb. Any ideas would be appreciated.  

They should have mentioned that you put the cap back on before you shut it off. It may blow some back into the recoverary tank. The sudden stop of the water pump releases the suction and splat, you better not be standing in front of it.  

BarneyFormula/WallaceRacing.com are correct - it's the distance between the vanes of the impeller and the divider plate - .030 to .060  between the vanes of the impeller and the divider plate. Pontiac Water Pump Divider plate, sleeves and gasket can all be found cheap at: tinindianperformance.com

Divider Plate:
#WP-001
$8.00
Pontiac Water Pump Sleeves
#WP-002
$13.00  

I just posted a very similar starter problem (rookie to this) as described by 84GP455 above, so I hope someone can add to my very limited knowledge. My GTO already has a separate solenoid on the fender well and the starter keeps frying anyway. Can anyone be more specific on the type of starter (mini?), solenoid, starter cable gauge, how to 'bypass' stock solenoid on the starter, etc.? Thanks.  

I heard with any pontiac engine 326+ the main problem is overheating. Why? Most of the time, when you get your Pontiac engine rebuilt, most forget to put the Water Pump divider plates in and this is a big oopsie!!! These things are really important but yes there are other ways to get the temp down but divider plates 90% of the time fix overheating