A little update here. In the time since my tow truck ride in May that was precipitated by difficulty hot starting and a carb backfire, it has been my goal to address that issue. I now think I have it sorted out after making a few changes. The first thing I did was check the carb float levels, and they were close'ish, but the front bowl was a hair high. After that, I noticed that my fuel pressure was also a bit on the high side, reading at 9psi hot idle. So I dropped the fuel pressure down to 7psi hot idle. According to Holley, they want to see 5-7psi, so 7psi at idle should leave room for a pressure drop at WOT.
After doing that, my next order of business was to figure out just how much hood clearance I actually have for adding a carb spacer of some sort. I am running the Edelbrock Performer RPM high-rise dual-plane intake manifold and a 3 inch tall air filter element, so I thought I'd basically have no extra room under the hood. Turns out I still had about 2 inches of clearance between the tallest point on the air filter lid and the underside of the hood. I was shocked to find that I still had that much room to play with. So I ordered a half-inch phenolic carb spacer from Summit and put it on.
I am pleased to report that after the changes listed above, my hot start issue seems to be a thing of the past. I've had the car out in similar temp weather since the initial problem and it has not once given me any trouble starting up when the engine is fully heat soaked. It would struggle before when ambient temps were in the upper 70s to low 80s, and it's no problem now. The carb spacer does really make a difference, since when the engine is hot I can't touch the intake manifold for even a second without burning myself, but the carb is still cool enough to keep your hand on. We'll see how things go as I rack up more miles, but things are looking good so far.
I spent the evenings last week removing lots of fine scratches that were overlooked by my painter who did the final wet sanding the other month. He did remove 99% of the orange peel which is fantastic, but he left behind LOTS of fine scratches from his own sanding all over the car. The hood, trunk, roof, quarters, you name it. He's a nice guy and does decent work, but he's always behind schedule and rushes as a result. Anyhow, I have my own equipment and experience for paint correction, so I went over everything again myself.
Before
After
With paint correction now (mostly) out of the way, I took the GTO on its longest drive yet since restoration this past Saturday. I'm in the Seattle area, and my spouse and I took a ferry ride over to Vashon Island to cruise with some other Pontiac friends. A work friend of mine restored a '64 GTO convertible with her dad a few years ago, and she is friends with a family that owns a 50k original mile '67 Bonneville convertible. Good company!
We cruised the island for a while, got dinner, and visited the lighthouse. Everyone's cars looked and performed great, and there were lots of waves, thumbs up, and flashing lights as our convoy of mid-60s Pontiacs rolled down the road.
My GTO seems very happy from a mechanical standpoint. Engine is great, trans is great, suspension is great, and the 4-wheel disc brakes are a treat. I can't tell you how much I appreciate a consistent brake pedal and arrow-straight braking.
Now I just need to get rest of the trim on and tackle a few other odds & ends, but I'm really starting to build trust with the car.