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Discussion Starter · #1 ·
Hello! I know this topic has been discussed ad nausem but one more question, please. Car is 1967 400/335. Engine just fully rebuilt. Car ran hot before rebuild. Runs hot after rebuild. New 4 aluminum radiator. New EFI. New high volume water pump. Timing seems to be set optimally. Water wetter. Now that temps are getting warmer, runs hotter. At 55, temp around 210...but stopped at light or stop and go traffic, temp shoots up immediately to 230 or so....perhaps more but I haven't put myself in a position where it could. Electric fans didn't help. Tried various thermostats, didn't help. So, desperation. Has anyone tried waterless coolant like Evans? Any meaningful results? As always, thank you.
 

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1967 400ci/TH400
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Had same issue with my '67 / 400 ci / 335 HP - i used a "Cool Case" kit from Ames (new radiator, thermostat, fan, clutch and high flow water pump); also added overflow radiator. Runs cooler now.

The other issue is that my guages were not reading properly; many of them need really good ground to engine for proper reading (digital ones). If you have a Sniper EFI, does the computer water temp read the same as your other one? Mine didn't until i fix the ground issue.
 

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Discussion Starter · #3 ·
Thanks for the quick response. You're right about the OEM temp - way too high. But, the EFI readout looks realistic. May I ask what kinds of temps you are seeing now and the outside temp? Thank you!
 

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1967 400/400
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  1. Not all radiators are created equal. Cold Case and Be Cool, are top notch, professional products. The crap on Amazon is aluminum, and that's about it.
  2. High flow thermostat, and drill three 3/16 holes in it.
  3. Add an engine oil cooler. Cheap, easy, substantial benefits
 

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are you running ac pulleys ??? big crank small water pump
or is the water pump and crank pulleys the same size basically ?
they are different diameter than non ac ,,,, and provide more water pump rpm
 

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Not all electric fans are created equal as well. Do the fans have a shroud or are they just zip tied to the radiator? Whats the fans size and how many CFM do they pull?

Also Whats your idle and cruise timing set at?
 

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Hello! I know this topic has been discussed ad nausem but one more question, please. Car is 1967 400/335. Engine just fully rebuilt. Car ran hot before rebuild. Runs hot after rebuild. New 4 aluminum radiator. New EFI. New high volume water pump. Timing seems to be set optimally. Water wetter. Now that temps are getting warmer, runs hotter. At 55, temp around 210...but stopped at light or stop and go traffic, temp shoots up immediately to 230 or so....perhaps more but I haven't put myself in a position where it could. Electric fans didn't help. Tried various thermostats, didn't help. So, desperation. Has anyone tried waterless coolant like Evans? Any meaningful results? As always, thank you.
I fought this same problem on a 66 389. Went through everything like you water pump,radiator, water wetter etc. Finally found 2 things;1 Ran thermal imaging over engine and radiator- found center cores of radiator was blocked off with solder from factory, water flowed great but wasn't allowed to flow down through cores for more cooling. 2. Be sure plates behind water pump are set close to impeller . Mine were 5/16" and that was to much. I put the one with the large hole between 2 pieces of 1"x8" and squeezed it down until the impeller would almost rubbed. Then the car ran very cool.
 

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1971 GTO resto mod. Modified 428 HO, 4 sp (built by midwest muncie) Dana 60, 3.55 rear
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There are so many different things that can cause high temps.. Bear mentioned on problem that is often over looked..
Another issue is sometimes the one of the sleeves (or both) gets left out between the water pump and timing chain cover.
142219

Is your fan shroud installed?
Checking your temp at the thermostat housing with a laser thermometer will help trouble shoot. (as well as other places on the engine and radiator)
You mentioned electric fans.. My experience with those has been horrible at best..
A good mechanical fan with a good fan clutch and fan shroud should be all you need..
Another possibility is a faulty water temp sending unit..
there are lots of places to check.
Can you upload a pic of your engine compartment around the radiator/front of the engine?
 

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1971 GTO resto mod. Modified 428 HO, 4 sp (built by midwest muncie) Dana 60, 3.55 rear
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There are so many different things that can cause high temps.. Bear mentioned on problem that is often over looked..
Another issue is sometimes the one of the sleeves (or both) gets left out between the water pump and timing chain cover.
View attachment 142219
Is your fan shroud installed?
Checking your temp at the thermostat housing with a laser thermometer will help trouble shoot. (as well as other places on the engine and radiator)
You mentioned electric fans.. My experience with those has been horrible at best..
A good mechanical fan with a good fan clutch and fan shroud should be all you need..
Another possibility is a faulty water temp sending unit..
there are lots of places to check.
Can you upload a pic of your engine compartment around the radiator/front of the engine?
Forget the part about the sleeves.. They only come into play on 11 bolt water pumps not used until 69. Unless you have an 11 bolt water pump.
 

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Hello! I know this topic has been discussed ad nausem but one more question, please. Car is 1967 400/335. Engine just fully rebuilt. Car ran hot before rebuild. Runs hot after rebuild. New 4 aluminum radiator. New EFI. New high volume water pump. Timing seems to be set optimally. Water wetter. Now that temps are getting warmer, runs hotter. At 55, temp around 210...but stopped at light or stop and go traffic, temp shoots up immediately to 230 or so....perhaps more but I haven't put myself in a position where it could. Electric fans didn't help. Tried various thermostats, didn't help. So, desperation. Has anyone tried waterless coolant like Evans? Any meaningful results? As always, thank you.
A lot of info, bit still not enough.

Did you rebuild the engine back to the stock 335HP rating, or go bigger?

Still use the "670" heads and stock compression?

Stock points distributor?


Gotta know EXACTLY what your initial timing is, what your total timing is, at what RPM total timing is achieved, and how much additional timing do you get from the vacuum advance can.

Let's start there and we can then move to the next round of questions. (y)
 

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67 should have the 8 bolt pump. There are 2 divider plates. the first one should be centered on the impeller, laterally, to split the flow in half ,left and right to the intake ports on the block. the rear should be tucked up tight as possible the the impeller.
stand the pump on its nose. Lay the plates ,on the pump ,in order.Take a good look at it . You will see what I am talking about.
I went through the same thing on my 64.
 

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Good advice all around, work the temp gun. Shrouds matter, and electric fans need shrouds too. Spiking at idle is directly related to air flow from fans, inadequate if it gets too hot...

a good temperature activated clutch fan properly shrouded may help. But like PJ said your timing matters especially at idle. Too retarded causes hotter exhaust and thereby heats up everything...a thermostat partially stuck can give you many issues too, if you open the system replace it. Even a new one can be bad.
 

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Discussion Starter · #16 ·
Have you tried a laser temp gauge? You can see if water is flowing through the radiator at temp and verify the temps on your oem gauge are realistic. They have lots of uses.
I have and readings are consistent with EFI reading. Thanks!
 

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Discussion Starter · #18 ·
  1. Not all radiators are created equal. Cold Case and Be Cool, are top notch, professional products. The crap on Amazon is aluminum, and that's about it.
  2. High flow thermostat, and drill three 3/16 holes in it.
  3. Add an engine oil cooler. Cheap, easy, substantial benefits
1. I have a Holley Frostbite 3 row, rated by Holley as capable of handling 700 hp. My engine is standard 400/335.
2. High flow thermostat. I've read various opinions about pro/con and am uncertain. I'm not refuting you but my logic is that hi flow has coolant more quickly pass through the radiator giving it less time to cool. Where am I wrong?
3. I had not thought of an engine oil cooler and like that idea very much. Looking into it!
Thank you. Much appreciated!
 

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1967 400/400
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There are MANY opinions, rituals, and practices when it comes to anything cars. Cooling is no exception. In my experience, a clean and well designed system always works well. And in my experience, when that isn't true, then something else is wrong.

I've heard that water pump impellers make a big difference with Pontiac. Are you using a good, name brand pump, or a parts chain rebuild?

As for the thermostat, bypass holes shouldnt make or break your system... However, as I mentioned, when all else is right, they can add to efficient operation. It's not likely that they will cure your issue.
 

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Discussion Starter · #20 ·
I fought this same problem on a 66 389. Went through everything like you water pump,radiator, water wetter etc. Finally found 2 things;1 Ran thermal imaging over engine and radiator- found center cores of radiator was blocked off with solder from factory, water flowed great but wasn't allowed to flow down through cores for more cooling. 2. Be sure plates behind water pump are set close to impeller . Mine were 5/16" and that was to much. I put the one with the large hole between 2 pieces of 1"x8" and squeezed it down until the impeller would almost rubbed. Then the car ran very cool.
The plates have been checked and rechecked but I don't know the distance from the impeller off hand. Would you help me out with the 2 pieces of 1" x 8"? I don't follow that. Thank you!
 
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