I have noticed that my small engine 1 1/2 litre 1948 MK IV is sounding different with the last couple of tanks of fuel, and I know that in recent times the fuels in the UK are changing in a bid to go “green”. More additives are seemingly going in by the suppliers before it is dispensed at the fuel pump. Whilst my engine seems well set up and serviced to the normal Jaguar specifications the tappet noise appears slightly louder and I do hear more pinking. A few years ago the advice on this web-site was that owners of this era of leaded fuel cars should not unduly worry about using modern unleaded fuel, or perhaps if they did worry to add a lead replacement additive in each tank full of fuel.
Has anyone experienced this more as a recent problem with unleaded fuel? If so are there any new and better or recommended lead additives that have been tried in recent months? And if not going the additive route is there any merit (or warning) in adjusting the tappet gaps (normally 0.012"), timing, points, etc to compensate. Excess noise in my mind perhaps means potential problems - or is it simply a case that the new fuels make the engine play a different tune !!
My engine is original with no modifications or re-work, and I would prefer to keep it that way.