[geeteeohguy]

I see you spent a ton of money on the cooling system, but did you set the clearance of the water pump impeller to the divider plate? Incorrect clearance here is the number one reason for a Pontiac to run hot. You want an eighth of an inch or less of a gap here.....if it's out at a quarter of an inch, the water pump cannot do its job and it will run hot. Also, a cast-impeller water pump will cool better than one with a stamped steel impeller. Many threads here on this forum on how to check and set this crucial clearance. Beautiful car, BTW!

[M1Lover]

Man, that's a gorgeous car. You paid top $$ but it sure looks like it.
On the other end of the spectrum, I bought my '66 242 car (also from the Pontiac, MI factory) locally for $3500 and I'm not sure if it had been free that it would have been a good deal. That's not true, actually, I got far more than that in good, OEM parts. By the time I'm done, using a '66 LeMans for parts, doing most of the work myself, I'll likely have upwards of $25k in it and a helluva lot of time (Time=$$). The money is going to come from somewhere to get to the level you've purchased.
On the "Running Hot" topic, I'm dealing with that on my '67 Grand Prix with its original 400. I went the same route as you have, almost, but used a FlowKooler pump, new HD clutch fan from NAPA, and for stock looks had my radiator rebuilt with a 4 row high-efficiency copper/brass core. When I first put my new water pump in, I bought some new SS divider plates off of E-Pay. I never gave it another thought till I noticed that my car's temp just kept cranking right up there to 220, on a warm day, but not working it hard. Just pulled it down again while redoing the radiator and I'll bet the gap between the impeller and plate WAS close to .250" I did the "field modification" on my bench and closed it up significantly. Closer to .0625" all the way around. I'm waiting on the rubber mount insulators for the radiator from AMES (should be here TODAY) and I'll report back on the temperature study as soon as I've got it back together.
Enjoy that GTO, its sure a beauty. I hope mine comes out close to that nice.

[Mister Pontiac]

Originally Posted by PTS

I should have brought a restro mod. Once I took delivery of the GTO and running it for about 10 miles the temperature slowly went up to 230 and climbing. So I invested about $1000 to try to repair that problem. Started with the basics, thermostat, high volume water pump, hoses, clutch fan, changing mechanical water temperature gauge (which was off by +5) and then followed by a custom 5 core aluminum radiator. that got it down to 215. Still not satisfied. Then I had the rear ratio changed from 433 to 336. Now we are at 210 at an additional $750. Now living in TEXAS you need air conditioning. Class Air Conditioning kit ($1900) , pulley, belts, Freon at $2100. I did the installation. Now with the A/Con I run about 215. Not that bad but I would be happier at 200. Of coarse you need FM radio. installed a Classic Car stereo system at $500. After reading some forums maybe the reason of the high temperature is the 67 400 block with 389, heads,intake and exhaust manifolds. The car runs fine and sounds good. I do not like the turn down pipe from exhaust manifold at 2 inches.Whats next? This is starting to be more expensive that a boat.

Yes indeed, beautiful 66! Sounds like you’ve made some nice improvements already.

The aforementioned advice on checking the water pump divider clearance is good advice. The rear gear swap likely helped immensely too. Other than that, 215 degrees on a hot day with a/c on is no big deal. I’d drive that all day long.

There are exhaust kits up to 3” diameter that you can install (pypes, etc), so not sure what exactly you’re looking for there. 2.5” bolt on downpipes would be a nice upgrade and give a little more HP, but depending on how “hard” you’re driving it, i’m not sure how much improvement you’ll “feel.”

Enjoy that beauty!