RE: 9.5:1 comp and pinging Spitfire.
What year is your Spit? My Midget (with a 1296 Spit engine) used to ping very
badly even with static timing at 2 degrees AFTER TDC (specs are 10 before). I
tried verything so ended up rebuliding to remove carbon build up.
Now no more ping but the ping was caused most probably by a vacuum leak in
an emissions pipe someone had removed and sealed badly on the intake manifold.
SO cheak VERY VERY carefully for intake leaks as they can occur in many places.
I do not think you should ping at 9.5:1. I thought this was the limit at which
normal regular gas could go??? A well respected friend in the MG racing game
has a B which he has at 9.5 or 10 :1 but does not ping with regular.
However, both he and I have an SK carb with static ignition set at 22 BTDC. I
think this carb can supply the fuel the car needs at this ignition setting at
the higher comp ratio.
You might try (1) Looking for intake leaks at the throttle shafts, manifold
gasgets, any emission fitting anywhere on the intake system, etc.
(2) Make the mixture alittle richer
(3) Use cooler plugs
Of course if the needle in the carbs is not calibrated correctly for
your engine this could cause lean spots, if your dizzy is not working correctly
it might give you wierd advance, if you were out on your comp ratio you might
be running more than 9.5:1.
Let us know what happends. Cheers Dennis Wilson
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