Whats's the best petrol for a Side Valve engine?

[oliver-morrisminor]

I am soon to commision the sidevalve engine in my Series MM.

I was wondering about what Octane fuel was best?

Seeing that when the engines where originally made
all you could get was a low octane fuel, I was wondering
is the standard unleaded 92 Octane was OK,
or I have been told that with older overhead valve engines
that a 96 or 98 Octane is better.

Also I assume there is a need to use a lead additive as well?

What do the masses advise?

[mike.perry]

I found that with higher octain petrol I had fewer burnt out valves. Since I now have an unleaded engine with hardened valves, seats and guides that is no longer a problem and I use ordinary unleaded 95 Octain. With the compression ratio of a side valve there is no point in using anything higher

[oliver-morrisminor]

Hello again Mike,

My engine has not had the head modified with hardened seats,
so would you recommend the lead additive for my engine?

Thanks Oli

[mike.perry]

If you are doing high speed, high mileage runs then it probably is worth using additives but if you are just pootling around locally then I would not bother