Working out:
centre of pump spindle to centre of timing pin 25mm (approx)
9mm - 8.5mm = 0.5mm
Angle of degrees per 0.5mm = 1.14576 degrees
So moving from the standard 9mm timing pin to 8.5mm equates to an advance over standard settings of 1.14576 degrees
Left hand edge of timing pin:
Standard timing with 9mm timing pin will be 19.7988 degrees BTDC
Tweaked timing with 8.5mm timing pin will be 18.6531 degrees BTDC
Tweaked timing with 8mm timing pin will be 17.5073 degrees BTDC
Centre of timing pin:
Standard timing with 9mm timing pin will be 14.6428 degrees BTDC
Tweaked timing with 8.5mm timing pin will be 13.4970 degrees BTDC
Tweaked timing with 8mm timing pin will be 12.3512 degrees BTDC
Right hand edge of timing pin:
Standard timing with 9mm timing pin will be 9.4869 degrees BTDC
Tweaked timing with 8.5mm timing pin will be 8.3411 degrees BTDC
Tweaked timing with 8mm timing pin will be 7.1953 degrees BTDC