[CSX 4027]

It does have an effect but I do not remember which way or why. I will ask my builder tomorrow.
Regardless, we still need all the other info to make a real judgement.
I have never seen a 427 run more than 38 degrees and I would love to see the plugs after the dyno session.
The more efficient the motor, the less the need for advance. My 427 ran 32 and my cup motor runs 32. 40 sound dangerous to me but I guess there are a lot of other variables to this story.
Please have the whole sheet with all the columns posted.