Creamie,
I've just learned something new, I didn't need to modify all those Jag cylinder heads to run on unleaded, and the blokes who supplied the new valve seats and valves (of clearly different material to older exhaust valves) was obviously deluded by Jaguar supplying these new p/ns for "unleaded" conversion.
It was all a big con!!
Likewise, those very real examples of "hammered" valve seats I have seen are nothing to do with running unleaded, but the problem mysteriously does not reoccur if we modify the cylinder heads with the new exhaust valves and valve seats.
From a BP data sheet.
UNLEADED WILL NOT HARM YOUR ENGINE
Unleaded Petrol is perfectly suitable for those engines capable of converting from Leaded to Unleaded. These engines do not require lead for exhaust valve seat lubrication and are satisfied by the lower octane of Regular Unleaded Petrol.
Old leaded engines not on this list either require lead for valve seat lubrication or require a higher octane fuel.
https://www.google.com/url?sa=t&rct=...3,d.dGIhttp://
Another con job by the RACQ:
Unleaded Petrol and Pre-1986 Cars | Motoring | RACQ
Now, perhaps, we could start a discussion on flame propagation rates of burning, versus pre-ignition versus detonation and the significance of differing octane ratings, and the contributions of various components of the typical leaded and unleaded fuels, and the effects of different fuel air ratios. (ie What does 100/130 for an aviation fuel mean).
Oh Boy, this takes me right back to the test engine for determining octane ratings we had in the basement of the old Engineering School at Sydney Uni. --- that WAS a long tome ago --- but, mysteriously, the ASTM D 910 Aviation Gasoline specification for leaded, of the present day, looks remarkably like the one we had then??
Tootle pip!!