I have done minimal unleaded conversion to my UK 4* 98 octain drinking
beast. I went to the grean pump insted of the red one, and tryed to avoid
the super unleaded pump.
Go for the higher 9.0, because its easy, you just put in flat UK pistons.
You can always skim later. With the realy ceap unleaded, UK 91 octain, I
think thats US 87 I only get pinking with the distributer set 2deg ahead of
normal at 12 deg BTDC. Thats including my warn distributer which scatters
the spark +- 2deg anyway. When I had the electronic ignition distributer in
I had absolutly know problems, could run it at 14deg BTDC, but I then found
it had the wrong advance not enough at the top end.
A good cure for pinking it to fit cooler plugs, or electonic ignition, cool
air intake ducking, then you might find you need to retard the ingition.
Remember air rams dont work in Spitfires because of the constant depression
carbs, instead you have to setup a cool air stream which channels air past
the carb for it to take what it needs.
So I recon you wont have any problems with the conversion.
James
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