Lowering the LSA doesn't always mean you'll get a nasty idle.
Overlap is what you hear and just because a cam is a 104, 106, or 108 (or anything in between) LSA, doesn't mean it will have a nasty idle.
I can grind a very tight advertised duration, small .050" duration camshaft on a 104 LSA and it will not thump. Or.....I can grind a very large advertised duration on a 114 LSA and it will sound completely nasty.
Multiple variables play into how much overlap (sound) you have. The LSA is just one of them and isn't the major proponent.
In addition to all of that, it's generally thought of that a 110 LSA is a "good street cam", a 112-114 is "an EFI cam", a 108 is a "drag race cam" and a 106 is a "circle track cam". Those thoughts and ways of thinking couldn't be further from actuality/reality. Widening the LSA doesn't always mean it will have a smooth idle and narrowing the LSA doesn't always mean it will have a rowdy idle. My pulling truck camshafts are on 119-121 lobe separation angles and sound like the engine is leaving the face of the earth.
Thumpr cams sound like they do not just because the LSA is on a 107, but because the advertised durations are very high as well. These cams have overlap numbers in the 90's. They are made for pure sound, not efficiency or horsepower. As a matter of fact, for anything but the most horrible performing factory heads, they are putting more horsepower out the exhaust than making it usable.
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