Unleaded fuel

[Kevin-G]

I'm sure that it's been asked before, but what is the collected opinion on running a standard 1098 minor engine on unleaded fuel?

I tried searching but I could not find a definitive answer.

Thanks

[kennatt]

just do it,all it causes is valve seat regression and exhaust valve burning ,but only after very high milage and constant high speed(If you can get one to high speed ) motorway use. Do the head with hardened seat inserts when the head/valves have gone beyond re seating'/grinding or when you decide to have the head off for refurb .I have run my 55s11 ever since leaded was removed,not had a problem. Def not worth modifying head just for the sake of doing it. And don't bother with additives don't really have much effect except mentally your "head "

[oliver90owner]

Do you mean standard as in state of tune or original (without fitted valve seats)?

Former - fuel consumption would be marginally higher. Requires different timing setting.

Latter - with original valve seats - as kennatt.

Sodium filled exhaust valves as well as hard seats would likely be overkill, but that would remove any problem of burned valves and seats.

[Monty-4]

As above the common wisdom is that it's fine if you're not doing high and fast mileage.

If I recall correctly, Roy (RIP), recommended increasing the tappet clearances on the exhaust valves to 15 thou rather than 12 thou. You may also want to tweak the timing.