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66 GTO 455 overheating

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thor7726:
Hey Guys,

I put my freshly rebuilt 1970 455 with quadrajet 7040268 in my 66 GTO and at idle or traffic driving it slowly heats up until and will overheat in a few minutes.  Driving down the road it runs great at 180-200.  Here is what I got and have checked:

A.) no 64' 87cc heads
B.) 9.7 compression Ratio
C.) 93 octane
D.) High cylinder deck to piston quench at 0.018"
E.) Bored 0.03" over
F.) Ram air 4 cam
G.) 4 speed


1.) Water pump replaced and with baffle close to impeller.
2.) 66 4 core radiator, tested good for flow and pressure.
3.) 66 declutching fan with half in half out of shroud.
4.) New belts that are not slipping.
5.) Tried both 180F and 160F thermostat new
6.) New hoses with inner springs to keep from collapsing.
7.) 66 'pan cake' air filter.  (Probably restrictive)
8.) 2" duals (Restrictive)

After all of this could it be the carb is out of tune and causing it to run hot?  Sorry for the long post but I wanted to show that I've been through most of the obvious with the cooling system and now wondering if its the carb running lean or rich and what to do about it.  Its my first Quadrajet and I got my parts from Cliff and I have barley touched the carb and it runs great, idles, responsive, etc  Super impressed with the parts! 

Thanks,
Pete

Jeffs68:
What is your initial timing set at? Vacuum advance hooked up to manifold vacuum, vacuum switch or to the carb somewhere?

Unlikely your carb is the overheating issue.

Even if the fan clutch is new, I've seen out of the box units faulty.

Not sure about the Goats, but are all the filler panels around the shroud in place?

When you say overheating, what is the temperature rising to?

Not uncommon for Pontiacs to run 220-230 in traffic/idling.

Hillbillyenginering:
I have friend at work who's 70 gto, 400 12/1 comp. Was overheating. Tried everything. New radiator, 160 stat, fan clutch, high flow water pump. Ended up being a bad distributor. Put in an OK aftermarket for China. And no more over heating.
The dyno guy said to run 91 octane pump gas. Open up the jets a little and let the corn help cool it.
Seems to have fixed it

Spudboy:
   Like what jeffs68 said, what do consider overheating? Sounds like my 70 Judge. Will run 180 going down the road but will run anywhere between 200 to 220 in town, depending on the outside temps. And I've been down the same checklist of
fixes you have. I make it a point to ask other Pontiac owners about the temps their cars run. Rarely, do I find a Pontiac that will run under 200 all the time. 

qjetsrule:
I read a good article which addressed this exact problem, everything was right with the car but same symptoms. I believe it was a GTO also. The fix was a smaller water pump pulley which circulated more water in traffic. Good luck.

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