Have silicone spark plug leads fitted but they are too fat for the plastic retainers that clip into the fan shroud. Tried filing them but there is not much plastic to file. Anyone out there already solved this problem?

If its just the plastic that holds the leads together... you can buy new universal ones from your auto parts store.

Don't use silicon leads on a vw air cooled motor unless u want problems

I have heard this before but when asking for more information havn't had anyone be able to be specific about what problems they cause. Personally I don't understand what the difference is between air and water cooled as far as providing power to the spark plugs but I am certainly no expert so would welcome your input

The difference is the ignition system already has enough resistance built in with a 5k ohm rotor button. When you add the high resistance of the silicone ignition leads (designed for a zero resistance rotor) you are adding too much resistance to the system for the coil which WILL die.

Thanks Matt. An explanation at last. The guy who made the leads said it depends on what model 009 (genuine etc) I have as to what resistance is in the rotor button. Also, the leads he made are about 2000 ohm resistance which he reckons is less than the standard leads/resistor ends. So hopefully my old GT40 won't croak.

Silicon leads tend to cross fire and break down much quicker in the air cooled engine bay with the extreme temps @ the cylinder head,
also the high resistance is not helpful as has already been pointed out.

Thanks. What sort of leads should I be using and where are they readily available?

std vw plug end are 1k ohm copper leads are zero
the rotors vary between 1 to 5k ohm
anyone who sells silicon leads for an air cooled

just used std ones unless you are using EFI then u must use SPIRAL core silicon