So here is my theory: My 26 T came with an 8 volt battery and it is burning out the ignition system on a Texas T Distributor.
The rest of the story: It had the motor and transmission rebuilt about 12 years ago and then sat for 10 years. Just before I bought it the seller put a new 8 volt battery in it. The rebuild included a Z Head, so I assume they used the 8 volt to overcome the higher compression. I'm aware that this should not be needed, but I never heard of an 8 volt causing problems on the old tractors I've been around, so it didn't bother me. Anyway, it burned two sets of points on the Texas T Distributor. I replaced the condenser, and it still burned points. Finally, the engine cut out twice in one day, so I thought I narrowed it to the coil. I put a new coil on and it ran like a top.....at least for several hundred miles. Then it started burning points again and suddenly stalled yesterday. It restarted after a quick point clean up and re-gaping. It has 8 volts at the positive post on the coil with the key on (generator is fully charging the battery and has an 8 volt voltage regulator)
Before I spend the money buying a new 6 volt battery and new voltage regulator does my theory make sense. It seems plausible to me that the couple extra volts might be arching at the points. Luckily it has 00 cables, so a conversion back to the correct battery should be simple... but I'm frugal.
I have been running 8 volt batteries in all my 6 volt cars and trucks since the 70s with on problems. I don't think points care what the voltage is. I had a truck in the mid 70s that would eat points every couple hundred miles. It ended up being a bad distributor. Rebuilt it with new bushings and problem solved.
I have been told it's hard to buy a quality condenser now? Bud.
Do you have a resistor in the circuit or perhaps the coil has a built in resistor? You're cooking the points because the full battery voltage is going across them. An ignition resistor lowers the voltage as it heats up increasing point life. Points do care what the voltage is and will tell you so by frying if it's high. I don't know if a coil with an internal resistor will cause points to burn if the resistor fails. I believe the coil will quit if the resistor goes but you say you ran OK for miles then started burning point again so who knows. If the coil has an internal resistor it'll be marked on the coil case. I suggest you look to see if it says so. One last thing: changing the bushings in a distributor will not stop points from burning.
Try a ignition resistor for a 32-48 Ford. It is designed to drop the voltage about 2 volts. I know on those cars if you bypass this resistor you will get very short point life
the ground is bad between the battery and the engine
replace the ground wire from the battery to the frame and make sure there's a ground wire between the frame and the motor
file the connections where the grounds connect
it may look good but it's not good enough so the generator over charges the system and burns out the confessor
I'm betting it runs fine with new points and condensor until you shut it off and try to restart it then it burns out the points and condensor
this drove me crazy on my John Deere until my dad explained the problem to me
all fixed after burning out several sets
If you run off an 8 volt battery I would recommend you buy a new 12 volt coil. Guys I know use 12 volt coils with their 8 volt set up.
Get one for a '67 or later Volkswagen or MGB. They are 12 volt with built in resister.
If you insist on running a 6 volt coil you must not have much more than 4 volts at the coil as posted above. You can use a '33 to 48 Ford V8 resister.
Better to keep it 6 volts and get rid of the 8 volt battery in my opinion, although some have used 8 volt batteries in 6 volt cars and have no problems, lncluding never burning out bulbs.
Do you have a ground wire from the distributor to the block? Distributor grounding is a well documented problem with the Texas T distributor and probably others.
The coil says "no external resistor required." I did run a ground wire from the distributor to the block a while back, but that didn't really change anything. I don't have a ground strap from the block to the frame. I can one of those easy enough. Now that I slept on it I'm leaning towards going back to 6 volt just to save myself the pain of constant tinkering (I have other parts on this car to tinker on!). Thanks everyone!