Off the top of my head, I would be measuring everything, especially the bore.

-Might not be round
-Might not be cylindrical
-Might be too much clearance piston to wall
-Probably not because the skirt is real short and the pin real high allows it to shingle
-And even if the bore was good and round, over heat it, and it won't be after that....
-Piston squirters plugged?

'70 Cuda,...605 EFI Hemi Street Car (6.20 best pass, 1.33 60ft)
https://www.youtube.com/watch?v=WYw6RA-k5Bk (6.25 at 108.75mph from inside car)
https://www.youtube.com/watch?v=3zQEb9uxFng (6.25 at 108mph from outside car)
https://www.youtube.com/watch?v=JCvfzsC4NgM (9.9)

'66 Barracuda AWB Stretched nose Blown 440 Car in build stage

'71 Duster Drag Car 400 Low Deck 512 best 6.002 at 115.44mph
https://www.youtube.com/watch?v=Znuo3jMUXTk