I have since discovered that the 'thumping' on starting is actually my Weber Carb backfiring. Why does this happen? It only does it about once a month and the car runs fine otherwise. Any suggs?
Su
Carb backfires
dont panic !
Get the engine timing checked first off,if this is O.K you need to do a compression test on each cylinder to check none of the inlet valves are sticking open,these would be the most commen things ,I suspect it will be you ignition timing ,does the car make a metallic tinking sound when you accelarate?If it does this is called pinking and means the timing is out ,let me know if this helps, its quite difficult to diagnose problems with out haveing the car to look at but i'll do my best,Mark;O)