Not Ranked
Paul,
A few observations to add to the discussion. Be forewarned I run EFI so have no direct experience (except #3 LOL).
1) Lobe separation is a factor in designing a cam for Webers to minimize fuel "standoff" above their venturis. The internet says 108-110 is a good range. Less seems to give problems, more may reduce power.
2) Backfiring on deceleration is not usually associated with intake vacuum leakage. It is much more often a result of an exhaust header flange leak, either at the head, or at the collector. Don't think it is usually a carb problem.
3) A friend used platinum plugs believing the more expensive plug would be better. He had a backfire usually on startup that could be heard for a mile. Changing to normal copper electrode plugs eliminated that backfire.
Just sayin...
Tom
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Wells's law of engine size: If it matters what gear you're in, the engine's too small!
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