# 67 GTO running warm at highway speeds



## brock5ga (Sep 29, 2008)

Hi guys,
I read the post about GTO overheating and it seems I have checked all of this. My problem may be normal. I have had my 67 GTO for about 3 years and it has the factory idiot light. When I bought the car, it had been sitting for several years. 67 GTO, standard 400 4bbl, dual gate auto, 54k original miles. When I drove the car home, the next drive my windshield fogged. I bypassed the heater core and ordered a new one. I continued to drive the car for about a year off and on and then let it sit until I moved. When I moved, I drove the car and then noticed a puddle under the radiator. Not at all surprising for a 40 year old vehicle (I have a few leaks and rattles myself). This is a factory AC car. I ordered the radiator, (3 flu desert cool I believe with side supports) which took three months. In the meantime, I replaced the heater core and AC evaporator, which was drenched in oil. I installed a Mr. Gasket 160 deg hi flo t-stat and a Summit mechanical gauge set. When I drove the car, the temp would get up to about 210 deg at 70-75 mph cruising for a while. As I was waiting for a seal kit for the A6 compressor, I replaced the t-stat with a Stant 180 deg standard t-stat and removed the a/c condensor, straightened and cleaned the fins to ensure there were no flow restrictions, and rechecked. The gauge would go to about 185 deg and drop to 160 deg. You could see the t-stat cycle about 3 times and then steady out at about 190 deg. The car would still go to about 210 deg at 70-75 cruising and cool back to 195-200 deg when back in traffic. It has been my experience that this is usually too much flow and the water is not staying  in the radiator long enough to cool. The total timing advance is about 38-42 deg if I remember correctly. I removed the water pump and thermostat and ran a video borescope through the water jackets in the side of the block through the timing cover ports. These appear clear. The 2 piece diverter plate is in good shape, with only one small pinhole at the top, and not a lot of corrosion at all. I have a new stainless plate to replace it with. I locked the water pump impeller in a vise and tried to turn it, and it would not turn. No signs of the impeller slipping on the shaft when it is hot. I still have the water pump off of the vehicle and the t-stat out, as I have some honey-dos to complete before I can return to my baby. I have also grabbed the crank pulley by hand with the water pump off and the timing chain does not appear to have a lot of play. I will check further before reinstalling. The car seems to have plenty of power and does not seem to be running lean. It is not blowing black smoke, has plenty of throttle response at highway speed, but does have a little spark rattle at light acceleration or maintaining on an incline at highway speeds. Any input would be greatly appreciated. Maybe I should just hook up the idiot light again and the problem will go away. It never ran hot before I connected those darn gauges!!! Thanks, Troy


----------



## brock5ga (Sep 29, 2008)

*Additional info:*

I have also changed to an HEI distributor and added an external coolant tank. The tank does not show signs of leakage or no signs of head gasket issues or cracked head issues, though I have not checked the cooling system for combustion gases.


----------



## Rukee (Feb 8, 2007)

Timing should be set to a max of 36* total at about 2500-3000rpm.
Even at 36* I still get some pinging, so mine is backed off alittle more then that.


----------



## geeteeohguy (Feb 2, 2008)

The high temps will cause the ping, also. Old GTO's seem to like to run around 200 plus degrees going down the road in the summertime. I've had many, and none of them run at 180 degrees. It sounds like you've checked all the bases and know what you're doing.....my next step wh=ould be water wetter. If you're not spewing coolant into the overflow, you're not actually overheating. A friend of mine had a '67 with AC and an automatic, and the car would run 215 all day long in the summer.....it never did overheat, though. Good luck!!!
Jeff


----------



## brock5ga (Sep 29, 2008)

Thanks for the input. I know 210 deg isn't enough to do damage, I was just trying to head off a problem before it started. Everything I have been hearing here and elsewhere is this is normal. Maybe I can get a chance to get this thing back together in a couple of weeks and tweek the timing. My compressor seal kit just arrived so I can reseal and recharge that. Looking forward to enjoying the car again!!


----------



## Eric Animal (Oct 28, 2007)

My 67 with auto and factory A/C runs 210-215 all day with the A/C. maybe that's just the way it is.....Eric


----------



## Pontiac Tempest Cstm (Jun 18, 2008)

my 65 used to runat 210-220 on hot days.i installed a mr.gasket thermostat not it runs at 200 on hot days and 180 on cool days.i also have an electric fan.i never did over heat either even from sitting in traffic on a 90+ humid nasty day.but its a 326.same block different bore.not sure if itll make that big of a difference in temp??


----------



## Pontiac Tempest Cstm (Jun 18, 2008)

p.s water wetter does work good.b4 the 160 thermostat i put it in and kpet the car at 200 on hot days.i also flushed the radiator b4my 160 and im sure it helped


----------



## brock5ga (Sep 29, 2008)

I am going to back the timing off when I get a chance to get this thing back together and try to eliminate some pinging. Another thing I was thinking of could be carbon buildup on the tops of the pistons. The old GM Top Engine Cleaner worked great, but I thing the EPA didn't like it too much and I can't find it anymore. Does anyone know of a source for this?


----------



## 05GTO (Oct 6, 2004)

brock5ga said:


> I am going to back the timing off when I get a chance to get this thing back together and try to eliminate some pinging. Another thing I was thinking of could be carbon buildup on the tops of the pistons. The old GM Top Engine Cleaner worked great, but I thing the EPA didn't like it too much and I can't find it anymore. Does anyone know of a source for this?


Try Sea Foam, you can find it at most auto parts stores.


----------

