Hot running problems- need help

[CT]

Hi I have a1969 4.2 series 2 coupe. It has recently started hot running problems. The engine was rebuilt c10k miles ago and I've just fitted a new coil and plugs to no avail. I'm running a 123 distributor from SC parts, The 3 x SUs had new diaphragms c 8 years ago ./ The cars starts no prob , runs revs and drives great for about 6 miles, then it starts to sort of miss, lose and regain power so I head home - when cold all starts Ok again and same happens. I can't work out if this is fuel or Electrics. But the HT leads are fairly new, and were bought with the 123- A HT /Plug spark in line checker show a very consistent and good spark- plugs all nice light brown. At least one carb float sticks if laid up for some time and needs a 'tap' to settle- then all OK. The fuel pump ticks merrily when starting cold and their does not seem to be any sludge in the filter bowl.
So any help welcome- might it be the 123? or where else would you start- fuel/carbs or electrics. Thanks you ideas very welcome to help. ps there is a small and old capacitor thing from the + on the coil - assumed this is an old radio suppressor but not sure-never touched it ! Regards CT

[Jack the lad]

Hi, its just a possibility that your tank vent is blocked, next time it does the miss-fire bit, pull up and remove and re-fit the tank filler cap, listen for a sucking noise as you do so. If it then runs fine for another 6 miles you've cracked it, clear out the tank vent and alls well. Some locking caps come without a vent and seal the tank filler completely. Good luck with it, cheers, Jack.

[1954Etype]

Check your fuel lines aren't collapsing. I have seen a lot of cars where the rubber line has gone soft or been replaced with the wrong type. Run the car with the boot boards out so you can hear the fuel pump. If it is the standard SU, it will tick occassionally. If it is ticking all the time, address that issue first.

It sounds like the ballaster resistor for the coil that is left over.

[christopher storey]

Also, have a look at, and preferably substitute, your rotor arm. These have become notorious for developing conductivity when hot, with associated misfiring and eventual total stoppage unitl it all cools again

[CT]

Hi, its just a possibility that your tank vent is blocked, next time it does the miss-fire bit, pull up and remove and re-fit the tank filler cap, listen for a sucking noise as you do so. If it then runs fine for another 6 miles you've cracked it, clear out the tank vent and alls well. Some locking caps come without a vent and seal the tank filler completely. Good luck with it, cheers, Jack.

Thanks for ideas Jack - checked and fuel tank cap rubber is sticky and old so ordered new anyway and will check out you ideas over the weekend too- thanks you- will let you know . Regards CT[/code]

[CT]

Check your fuel lines aren't collapsing. I have seen a lot of cars where the rubber line has gone soft or been replaced with the wrong type. Run the car with the boot boards out so you can hear the fuel pump. If it is the standard SU, it will tick occassionally. If it is ticking all the time, address that issue first.

It sounds like the ballaster resistor for the coil that is left over.

Thanks1954ET, you will check these ideas too

[CT]

Also, have a look at, and preferably substitute, your rotor arm. These have become notorious for developing conductivity when hot, with associated misfiring and eventual total stoppage unitl it all cools again

Thanks Christopher- have checked cap and rotor and no signs of tracking or damage and all clean inside- but will source a new rotor arm anyway as you never know-unless the tank cap is blocked per Jack's idea - hopefully CT.