I did a back to back test many years ago testing both 16 volt and 12 volt batteries in my Daytona and the ET’s were exactly the same. And that was when I was young and dumb and didn’t run an alternator. Love my 12 volt battery and an alternator

1970 Duster
Edelbrock headed 408
5.984@112.52
422 Indy headed small block
5.982@112.56 mph
9.42@138.27

Livin and lovin life one day at a time