I have a 1966 GTO with a 67 428 with no extras
I believe the engine was bored 30 over when rebuilt
I have replaced the old radiator with a new standard size 4 line replacement rad. and a stock shourd. I can drive it around fine as long as I don't stop for a stop light too long then my temp.
goes up above 210. I make sure I turn it off before it goes too high. Will a high flow water pump help or should I go to electric fan and water pump and alum. radiator
Any help welcome
clifH  

What type of fan do you have on the engine a clutch fan or bolt on fan also what thermastat do you have in it.  

ya something too is make sure you dont have a old water pump... mine worked but didnt work well went out and bought a 50 dollar one and swapped it out and now my engine sits steady at 170 rarely goes up unless its 110 outside and even then it only goes 190 and stays... umm check your water pump though i know that when my car was doing what yours is id pop it into neutral and rev the engine to about 4-5 thousand rpm got a flex fan so much more wont do good but it pushed my water pump to work harder along with the fan check that stuff and listed to what pontiacman8 says when you give him your details... from what ive seen he knows his stuff  

I have a similair problem with my 65. The newly rebuilt 400 was bored 30. I installed a new replacement 4 core radiatior an aluminum high flow water pump, new clutch on the factory 7 blade 18" fan. Does fine on the road but warms to 200 plus at a stand still. Even used a reinforced lower hose cause these high flow pumps will collapse a molded type. Used some of the water wetter stuff that may have made a small difference??????????  

65pmdgto1 what thermastat are you using.  

I'm using a full flow 180 degree stat.  

180 190 are good temps for that thermo even a little less like i said make sure you dont have a bunk water pump... i dont know what pontiac man will tell you but im telling you make sure that water pump you got is good cause i just got done fighting with that same problem with my deal overheating...

ps what fan you using still dont see a response for the question posted earlier? is it flex or something else  

I think the problem is the fan I would use a bolt on fan from flex-a-lite. A buddy of mine had that problem and the clutch fan was just not pull enough air at idle.  

Thanks for everyone responce to my 66 GTO overheating!!
I think there is a 180 thermostat inthe car and I just changed from a non clutch flex fan to a wider blade stock looking fan that Summit Racing suggested to pull more air, I also added a bottle of wetter water but it didn't help much. I think because of cost I will get a higher flow water pump and change the thermostat to a better flow 160.
Thanks Everybody  

I have a 65 GTO,heating problem.I have put correct upper and lower rad hoses,Pont 7 blade fan,straight5 blade fans,duralast waterpump which the say is a higher volume than stock, full fan shroud,aluminuum 4core,several other water pumps,wetter water still while sitting it will start to go up. Do you have any other suggestions? I've also moved the timing around abit.  Thanks Al  

What thermostat are you running in the engine and what temp. does the engine go up to.  

I think one of the other guys hit on the solution to a lot of these guys over heating problems. He force fed water in head heater hose until it flowed out the top of the manifold fitting for the sensor next to the thermostat housing. These motors must have an air lock problem in the design or the replacement head gaskets have something wrong. I wish I had my origanal head gaskets to look at but canned them after the rebuild. My 03 Bonneville has a little screw bleeder in the top of the thermostat housing, maybe these Pontiac guys know what they are doing. I'm temped to drill and tap a housing and see what happens.