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On E60+ I usually run up to 28 degrees on the LT4's before any modifiers( Humidity and IAT's) and 29 on the LT1's before any modifiers. Even in full humidity, the modifier pulls half a degree. Then if things heat up the logic will pull more timing. I choose the set this up like OEM logic. I know some tuners remove most of the logic and lock in on a lower number timing number for consistency. I'm not saying I am right or they are wrong. I just do things a little differently. I have quite a few cars running around on the street with this setup with no issues.
I've seen one reputable shop run up to 32 degrees on the dyno on the LT4's with E62. However, I'm sure they back it down once it's off the dyno. I can't imagine that living very well on the street.
If the car is boosted to the moon I'll back that number down to 26-27 depending on the setup. Cammed cars are a little different as well. So my above numbers are stock heads and stock cammed cars. Timing is ramped up on the LT4 from a lower value to a peak value at redline. The LT1's are a little different. They like more timing pre peak torque, then less timing during peak torque then more timing after peak torque. I don't desensitize the knock sensors either.
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