89 Fox 427
Slower than promised
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I just looked at my BBC Air-Gap.
The notch is 3/8" deep and it's more radiused than my RPM and the sides are radiused too.
The radius is pretty much a perfect half circle.
As I said above, the RPM is 9/16" deep
The Air-Gap is more than ten years newer than the RPM so they may have updated their ideas.
I think you have your answer.
Thanks for looking into that! Going with the 3/8 notch














