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Old 06-16-2013, 09:11 AM
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over heating pontiac 400

I have tried every obvious solution to my 67 pontiac gto 400 overheating. Top of motor was rebuilt 7 years ago after it blew a head gasket. The bottom was not touched. I'm thinking something was missed by not re-building the engine block.

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Old 06-16-2013, 09:29 AM
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Welcome to the forum, I see it's your first post.

I'm a Pontiac fanatic...had lots and still love them.

Listening to your situation, remember the block is almost 50 years old, water passages get plugged with crap.

Rebuild the bottom end, get a professional clean it up, hot tanking etc. If you've done everything else, all is good, a lower passage is plugged.

Ray
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Old 06-16-2013, 09:44 AM
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Quote:
Originally Posted by gold67gto View Post
I have tried every obvious solution to my 67 pontiac gto 400 overheating. Top of motor was rebuilt 7 years ago after it blew a head gasket. The bottom was not touched. I'm thinking something was missed by not re-building the engine block.
Tons of reasons for overheating.
First thing that comes to mind is a plugged radiator.
Have you checked the clearance of the water pump plates. That being a 67 has 2 individual plates that need to be correctly adjusted. The innermost plate needs to be as close to the water pump impeller as possible. The second plate is a flow divider and needs to be adjusted so it is centered with the water pump impeller as it "divides" the flow to each side of the motor.
Water pump pulleys can make a difference. If the W pump pulley is larger than the crank pulley, then it is underdriven and cooling will suffer at Idle and low rpm as coolant will flow slower and so will the airflow.
A missing fan shroud will cause a heating issue as will running a flex fan. They are junk IMHO, but some guys rave about them.
I just installed a summit brand radiator and it made a world of difference.
the price and quality was real good.
Look at them in the generic /measure to fit ones as they are preety inexspensive and are good quality. I was truly suprised. My 64 radiator was 169 bucks. I had to mod my fan shroud some, but being it isnt a concours resto I dont give a ratts posterior.
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Old 06-16-2013, 10:31 AM
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All good and valuable information Latech, I agree completely.

Just a short story, not it will confirm or deny the OP's problem and possible solution but.

3 years ago, a fellow that heard I liked Pontiac's came to me and asked if I would like to buy his 1969 428...it was over heating and thought maybe the block was cracked ...He was asking $100...bought it, for the heads if nothing else...took it apart, the heads where full of crap, the block was full of crap...no wonder it over heated, where ever there was supposed to be coolant, there was crap. Had it hot tanked, magnafluxed, all is good...I now have a good 428 ready for a project...all for $100 plus hot tanking and checking the block for cracks...standard bore as well.

Like I said, the information you passed on was great and should be looked into, I took the OP's word that all had been checked, leaving crap in the block.

Ray
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Old 06-16-2013, 01:21 PM
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When I had my block hot tanked, it had never been apart. It was pretty clean inside, but there were 2 metal rods in the cooling system , one on each side. I suspect they are in there as a leftover of the casting process, in which they support the sand core to make the mold.
I have also torn apart blocks that had tons of sludge in the cooling system. Made darn sure that was flushed out.
Maybe after the initial inspection process, the OP will flush his system to see if that helps. I would hate to have to take one apart just to boil it out in a vat.
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Old 06-16-2013, 03:02 PM
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here is what i did to get my pontiac to run 10 deg. cooler. the block cooling jackets were plugged with crud & radiator sealer so I rodded these out.

a lean running engine will run hotter so make sure your air\fuel ratio is rich enough. after rebuilding my qjet per ruggles recipe my engine was getting the fuel it needed based on the cam and it ran cooler.

lastly i run a 160 deg thermostat and my water pump divider plate is set up properly per hand's book. my fan shroud is not installed yet.
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