Ok so Im pondering here, at what compression level is the line drawn for regular premium gas & Racing gas?

 

Not really sure, but my '69 Thunderbird with a 429 is supposed to have around 10.5:1 compression, 360HP. The manual says to run 100 octane in it, but it now limps along with the crappy 91 octane.

 

To many variables to set a number. Cylinder design is the biggest, the tolerances of the build (Quench etc...) Then there is the cam, piston design, vehicle weight, gearing, intended use, tuner capability. Finally, there is the quality of the fuel itself. Racing fuels are not created equal either.
The masses seem to believe around 9.5:1. However there are production factory cars with 11.5 . Which is also about where I prefer to run on choice head designs 91 With my bikes I run 13-14:1. The vehicles in your sig could range from 9:1 to 11:1.

It is best to specify a motor and pull from sources on what they have done and why. Pay the most heed to those who have measured (cc'd), recite actual CR numbers, degreed cams etc...

 

Mike you should add Octane Boost to your tank. Continuing to run low octane without retarding the timing will burn pistons out. I would bump your metering jets up on the carb by a min of 5#, maybe even 10. This will also make it run better on pump gas. Went through the same things years ago on my 360 when my dad gave me the truck. Pinging constantly on pump gas and it was low compression.

Your engine also requires LEADED FUEL. You should also add a lead substitute to keep from damaging you valve guides and seats. Unless you have had your heads reworked.

Or get some 140 octane Aviation Fuel.

 

Right now, I run it with the timing retarded so it not pinging and actually runs pretty smooth. A while back I had sent the carb to Pony Carbs for a rebuild. Long tory, but never again. They told me pus others that the lead additive will actually gum up the carb. Since the Thunderbird only gets driven 1500-2000 miles a yer, I've been told not to worry unless I drive it hard. From what I've read the octane booster adds so little, it worthless to add it. I'd love to ron 100low lead aviation fuel in it, and can actually get it at the airport just a few miles from me. However, if I went on a trip, I'd have to do something else. Yes, head rework is in the future, but don't have the money right now.

 

9.5-10:1 is the max for pump gas. If you have E85 near you that would be good option. But the carb would have to be able to handle alcohol, will yield higher octane. Have no idea on what it will do to the valves.

 

Mikeb
Look at the CR issue and the lead requirements as two issues.
CR
The alchohol, Toluene or any other chemical will help handle the CR, but will most likely need tuning to use. Toluene works wonders, already in gas at the pump, likely in an octane booster, and its primary purpose is to raise octane level. Does have drawbacks and cautions with use and handling.

Fattening up the carb tune will cause more heartache than fix. Lowers combustion temps which helps valves and seats. But costs in engine life etc...

Lead,
I would not concern with the guides unless you decise to start racing it. I use amco45 guides and despize steel, but many use steel and are happy with it. yours are most likely loose enough to be fine.
Most importantly, you are aware and are not running the motor at higher power. It will run for many years as you are doing now. Just as thousands of other old car owners who cruise occasionally.

AVGAS is actually lower in BTUs than most automotive fuels, but it is also required to sit for 12 months in the tank without degredation. Given how little you drive the car. that could be a big advantage. Lot less "gumming" from old gas.

Enjoy that T-bird for us will ya