I decided to gap my piston rings tonight. This is a fresh build using a freshly bored 390 block & my existing 040 over L2291F's.
Slipped a top ring into No.1 and squared it with a piston. Gap is between 024-025. Put the second ring in & same deal. This seems excessive to me? Box says 040 but that is the vendors sticker which obscures part of the Hastings sticker. The Hastings sticker only has 4.050 & the ring sizes. I downloaded a QR code reader as that is visible & that came back with '2m574040' which suggests to me they are meant to be 040 over according to the original label. I even put a mic over the feeler gauge & of course no error there.
I then set about measuring bore & pistons. Measured pistons (well one) at 4.089 & the bore at 4.091, which is the .002 clearance we discussed so I can't see any errors there.
Is this gap too large? Ring box pics for shits & giggles below.
