# overheating 400 1967



## goat670 (Aug 10, 2008)

my 67 400 bored.30,670 heads,068 cam,slightly modified rochester 4bbl,equilivalant to a 6 core radiator, 195 and 160 tstat tried, wetter water,engine is very fresh,2 different fans,has shroud...10 minutes at idle gets to 210 degrees, and keeps going,driving is around 185 degrees,slow down or stop n go traffic gets 230-240 very quickly,....not sure divider plate is present,must take apart to see, beyond that anyone got some thoughts on how to cool it better!


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## Rukee (Feb 8, 2007)

Are you sure that`s the actual temp and it`s not just reading too high? Is that on the factory gauge? An aftermarket mechanical gauge?
And how do you get an equivalent to a 6 core radiator?


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## goat670 (Aug 10, 2008)

actual temp verified with laser.jegs temp gauge electrical sender, added tubes in core amd added more fins per square inch. supposed 25% more cooling ability.thanks for the interest.also toasted the transmission. complete overhaul. and may again be damaged after 40 min roadtest


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## 05GTO (Oct 6, 2004)

Try moving the fan closer to the radiator with a Mr. Gasket fan spacer, my 66 with a fresh rebuild was overheating and overflowing thru the cap until I installed a 2.25 inch spacer. I have them on both the 66 and 67 and have no overheating problems. One other thing to check would be to verify the t-stat is properly installed with the spring on the bottom. If that doesn't correct the problem, replace the water pump and divider plate. Also verify the lower radiator hose is not collasping.


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## 05GTO (Oct 6, 2004)

I just read on your other thread that you engine is a 72 400, is your water pump an 8 or an 11 bolt?


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## Eric Animal (Oct 28, 2007)

:agree Proper fan spacing,a tight shroud, and CORRECT DIVIDER PLATES,are very important. I have also had collapsed lower hose, make sure the spring is in it. Rare but, do you have an exhaust clog issue?


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## goat670 (Aug 10, 2008)

05GTO said:


> I just read on your other thread that you engine is a 72 400, is your water pump an 8 or an 11 bolt?


THE WATERPUMP HAS 8 MOUNTING BOLTS....72 BLOCK 67 MANIFOLDS,670 HEADS,67 INTAKE,67 TIMING COVER,,,IS THERE A COMPATIBILITY ISSUE WITH THE TIMING COVER.?.BY THE WAY,THE WATER PUMP DIVIDERS WERE THERE,HOWEVER THE WATER PUMP HAD THE ALUMINUM IMPELLER.SO I HAVE ORDERED THE CAST PUMP WITH CAST IMPELLERS,


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## goat670 (Aug 10, 2008)

No Exhaust Clog, Divider Plates Are There.are There More Than One Design For Divider Plates? Timing Cover Is 1967, Block Is A 72 400


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## goat670 (Aug 10, 2008)

Fan Is As Close To Inner Shroud As Possible With Spacer, Have To Check On That Spring In The Hose However, Tstat Is Ok,


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## 05GTO (Oct 6, 2004)

goat670 said:


> No Exhaust Clog, Divider Plates Are There.are There More Than One Design For Divider Plates? Timing Cover Is 1967, Block Is A 72 400


In early 69 pontiac improved the water pump design on the 400, they changed to a larger pump and improved the divider plates. Do you have the original 72 timing chain cover which uses a 11 bolt water pump?


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## goat670 (Aug 10, 2008)

05GTO said:


> In early 69 pontiac improved the water pump design on the 400, they changed to a larger pump and improved the divider plates. Do you have the original 72 timing chain cover which uses a 12 bolt water pump?


no i do not,and would prefer to use the existing 67 cover. i hope the new waterpump helps . should have done by this weekend, any thoughts on the most efficient fan, with maximum performance at idle and stop n go traffic.


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## Rukee (Feb 8, 2007)

The correct flex fan should do the trick.


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## DR Bird 67 (Sep 2, 2008)

I've had the exact same issue. First, Make sure you burp all of the air out of the cooling system. If that doesn't do it, consider a high volume water pump. Flow Kooler makes one -claimes 30% higher flow than OEM.


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## goat670 (Aug 10, 2008)

*exhaust*

ran it with open exhaust and went to 235 in the driveway in 12 minutes 








Eric Animal said:


> :agree Proper fan spacing,a tight shroud, and CORRECT DIVIDER PLATES,are very important. I have also had collapsed lower hose, make sure the spring is in it. Rare but, do you have an exhaust clog issue?


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## 67gteeoh (Dec 17, 2008)

I've been reading some articles regarding engine overheating. I've attached a link that it seems helped others with overheating. 

Why does my new 455 run hot? - PY Online Forums

One recommendation that I see mentioned alot is to overdrive the waterpump by installing a smaller dia pulley from an A/C car. Typically the A/C pulleys are 6.5" in dia and non air cars are around 8".

Hope it helps


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## Koppster (Jul 27, 2008)

67gteeoh said:


> I've been reading some articles regarding engine overheating. I've attached a link that it seems helped others with overheating.
> 
> Why does my new 455 run hot? - PY Online Forums
> 
> ...



That's interesting, I'll have to measure the pulley on my 64. It is a non-AC car but now that I've added the Vintage Air system, I might benefit from a little extra pump action...my pea brain would have never thought of that!:cheers

Thanks


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## 67gteeoh (Dec 17, 2008)

What I thought was also interesting in the other forum was the mention of the upper rad hose being higher than the radiator cap and how it_ could_ affect cooling flow and lend it's way to an overheating condition. 

I went to a cruise last weekend and the ambient temp was ~90+. On the way car ran around 190 (had a 180* stat). Once i got into town and hit the traffic lights, went up to 210-220 and it wouldn't come down much once I started going again. 

During the week, I was "tinkering" and replaced the upper hose and cut it down so it was lower than the rad cap. I also installed an Accel Highflow stat, 195*.

This weekend, temps in the mid 80's, cruised on the highway to a cruise a good 20+ miles at 65mph and the temp never got over 185*. Off the highway, stayed right around 190-195, stop and go traffic.

Same return trip home, temp at 185, hit a construction zone where traffic was bumper to bumper for ~ 1 1/2 miles, stop and go. My eyes were glued to the temp guage but temp went to 210 and stayed there. Once through traffic and back up to 65 mph it dropped to 185. Is it just coincedence.....could be, but I'm a happy camper now.

My GTO is a heater delete from the factory, so it has no additional heater core to provide a small amount of cooling...all radiator, 4 core, clutch fan w/shroud.


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## 67gteeoh (Dec 17, 2008)

For what it's worth, here's another what I call "Great Success stories" on fixes for overheating conditions....


Chalk up one more for the cast impeller. - PY Online Forums


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## 64tempest (Apr 20, 2009)

It could be a few things. Lack of water flow, lack of air flow or lack of cooling capacity in the radiator. I'd get it hot with the cap off and check the coolant flow at 200+ degrees. Maybe feel the front of the radiator for airflow. Also while it's hot, check the temp of the upper and lower hoses (careful of the fan). If they are close, the radiator is not dumping heat, either because of low airflow or it's clogged inside. If there's a big difference between the temps, the radiator is working but not enough of that cooled coolant is getting back into the engine.


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## alankieler (Nov 7, 2013)

*THE solution to Pontiac 400 overheating*



goat670 said:


> my 67 400 bored.30,670 heads,068 cam,slightly modified rochester 4bbl,equilivalant to a 6 core radiator, 195 and 160 tstat tried, wetter water,engine is very fresh,2 different fans,has shroud...10 minutes at idle gets to 210 degrees, and keeps going,driving is around 185 degrees,slow down or stop n go traffic gets 230-240 very quickly,....not sure divider plate is present,must take apart to see, beyond that anyone got some thoughts on how to cool it better!


Here is what you need to do: I have had the same issue with my 1967 GTO 400 H.O. 4-speed. I tried everything, then talked to a mechanic friend who suggested a Flowkooler water pump. I had already purchased a Flowkooler radiator, but had installed a stock water pump. I ordered the Flowkooler water pump for $129 and installed it. My idle temp went from 220+ to under 190, a full 30 degree reduction in stop and go traffic. Trust me, put one in and see instant cooler results.


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## geeteeohguy (Feb 2, 2008)

This is a 5 year old thread......


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## Rockinindian (Aug 5, 2021)

goat670 said:


> my 67 400 bored.30,670 heads,068 cam,slightly modified rochester 4bbl,equilivalant to a 6 core radiator, 195 and 160 tstat tried, wetter water,engine is very fresh,2 different fans,has shroud...10 minutes at idle gets to 210 degrees, and keeps going,driving is around 185 degrees,slow down or stop n go traffic gets 230-240 very quickly,....not sure divider plate is present,must take apart to see, beyond that anyone got some thoughts on how to cool it better!
> 
> Fan clutch NFG can be the culprit . They can appear to be spinning but the enternal thermostat that controls the hydrolic can bleed the pressure to the fins internally. If you have any performance parts causing more heat go with extreme duty.
> 
> ...


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