Old Gasoline / New gasoline - Rubber

 The formulation of gasoline has changed somewhat but the specific
gravity had not changed.
Most R series Avantis were designed to run on 95 Octane Prenmium gas
and may run poorly on todays gas.
Low compression heads are available for these engines and if you want
originality and have the correct heads , there are low compression 
pistons available (cut top).
Some of the new gas blends have chemicals in it that will destroy
the old rubber. 
A common problem with the Avanti is that the gas tank sits real high
and when the needle valve in the carburator sticks open, gas will
run out all over the floor of the garage floor and several Avantis
have burned that way.
Some people have installed electric valves to open only when the
ignition is on.
Replace the gas lines with new fuel line that can be used with
modern gas.
R.Kapteyn (rkapteyn@mcs.com) Feb 99