I have a T engine that is running very rough at high throttle. It runs fine at idle and med. speed. It has been running fine for several years after boring, valves/seats etc. I have done the following so far with no change.
1. New Timer
2. Coil Box was taken apart all solder joints and fingers checked. Has coil mounted switch and the connections were polished
3. New plugs
4. Spark Plug wires are a year old, none leaking or cross firing.
5. New wiring to timer
6. Rebuilt Carb /different one
7. Vacuum was checked it was steady and normal.
8. Compression was even on all cylinders at 48lbs
9. Intake was taken off and checked for cracks and bad gaskets.
10. Timer is not grounding out anywhere
11. Timer has been adjusted correctly and is advancing ok.
With the vac. and compression being good, I would not think that is was the valves. But that looks like that is what is next. I am open to any other ideas...
Larry
Did you change the old wood in the coil box when it was apart?
High voltage can make carbon traces that leads the sparks aside inside the wood when wet - and once formed, they never go away.
Weak valve springs?
Coil Box Wood?
Too Lean?
i.e. Fuel Flow, carb adjustment, float level, carb passages clean.
plug gap, coils checked and set on HCCT or strobo spark.
Running on battery or mag?
Not in any particular order. Just some ideas.
You don't mention your coils or what is powering them. I had a high speed miss that was cured by replacing the 2 coils that were not rebuilt yet. The missing only happened when running on mag. I replaced the capacitors in the 2 coils that I hadn't rebuilt yet and the missing stopped. My best guess is that the higher voltage from the mag was causing a problem with the old capacitors. Jim
I think that Doug is on the Money with his suggestion of fuel flow. Do you have a fuel filter? Anything that can restrict the fuel flow slightly will allow the car to run fine at the lower speeds where the fuel consumption is low, but it will starve out at high speeds when more fuel is required.
When the coil box was apart, I dusted it very lightly with glass beads. Wood is good and dry. Coils have been replaced with Patterson rebuilts. Runs rough on battery and mag. Valve springs were replaced a couple of years ago but, something may have happened to them. No fuel filter but runs freely from the tubing. The tank is clean but I will take the fuel filter apart and see if something is floating around. Larry
If you have your tank under the seat, a fuel filter may slow the fuel flow enough for rough running. Try open the petcock at the carb bowl and measure the flow - like how fast you can fill a pint can.
Remove the filter and run the car without and see how she does.