LONG-TERM BUT INTERMITTANT FIRING (?) PROBLEM ON CLIPPER

HARD TO DESCRIBE BUT SOUNDS LIKE ENGINE MISFIRES, STUTTERS, WITH KANGAROO JUMPS IN LOW GEAR/LOW SPEEDS PARTICULARLY.

WHAT ITS NOT:
NOT FUELTANK/CORROSION ISSUE - HAD THAT - FITTED NEW TANK 1-2 YRS AGO AND FUEL FILTER IS CLEAR.

WHAT'S BEEN REPLACED:
PLUGS / HT LEADS / DISTRIB CAP & ROTOR ARM/ COIL. (THERMOSTAT AS WELL REF APPARENT LINK TO TEMPERATURE/HEATING DIFFERENCE - MENTIONED BELOW).

WHAT MADE A DIFFERENCE:
DC & ROTOR ARM MADE AMAZING CHANGE - BACK TO NORMAL, BUT AFTER 2 WEEKS ALL STARTED AGAIN, THAT'S WHEN I CHANGED COIL AND ANOTHER NEW DC AND ARM - HIS TIME NO CHANGE.

WHAT'S KNOWN:
CAR IS A 1991 H CLIPPER WITH WEBER CONVERSION CARB AND HAS BEEN RUN DAILY BY ME FOR LAST 9 YRS, SERVICED TWICE A YEAR AND CURRENT AT 140,000 MLS.

THIS HAS BEEN GOING ON FOR NEARLY A YEAR SO NOTHING IS ACTUALLY BREAKING DOWN, AND IT STILL DRIVES DAILY. NO PATTERN TO WHEN PROBLEM COMES OR GOES. APPARENT ON MOST JOURNEYS SOMETIMES AT BEGINNING (COLD), MIDDLE OR END (WARMED UP), AT ALL SPEEDS AND SOMETIMES FOR PART OF OR WHOLE JOURNEY.  SOMETIMES I GET 2 DAYS WITH NOTHING AND SOMETIMES 2 DAYS OF CONSTANT SPLUTTERING, JUMPING. SEEMS TO MATCH WITH SLIGHT DROP IN WATER TEMP AND SLIGHT LOSS OF HEAT. THERMOSTAT CHANGED AND SYSTEM FLUSHED AND NEW COOLANT IN.

RECOGNISED VW SPECIALIST IS 'STUMPED' MAINLY DUE TO THE INTERMITTANT FEATURE OF IT. USUALLY RUNS FINE WHEN I PUT IT IN.

I'M NOT A MECHANIC AND DON'T PERSONALLY WORK ON CAR EXCEPT MINOR REPLACEMENTS ABOVE. ….. HELLPPP !!!!  
 :dontknow:  

Ignition amplifier?

About ?35 and located on the right underneath the plastic scuttle cover and next to the wiper motor. Ideal for getting wet and messing things up!

It seems it's the only ignition part you've not changed!

When mine failed on my clipper it caused the same issues you described - search for my old posts if it helps?

Even after testing my old one (it came back apparently with no faults) I replaced it and all was well again!

Cheers

Thanks to above reply - pm'd.

However, no change despite replacing the ignition amplifier.

Reluctant to keep changes things on guesswork but thinking next of the distributor.

Any other ideas out there ?

Thanks.

(PS realise this should actually be under Big Block carb engines …oops!)