So heres my situation:
2.5 common block, bored for 0.030" over pistons.
All 4 cylinders are within factory spec for taper and out of round.
#2, #3, and #4 measure less than 0.001" out of round.
#2, #3, and #4 measure less than 0.001" taper.
#2, #3, and #4 all measure between 3.474" and 3.475".
#1 is the problem child.
#1 measures 0.0015" out of round at the top, and 0.0019" taper.
This is because I did alot of honing to remove a scratch. Glad I did, otherwise option was to scrap the block and do alot of machining. Worked out fine and had good compression.
If it werent for that out of round, #1 would fit in with the other bores as far as being between 3.474" and 3.475". Most of the bore does. But just that one measurement at the top perpendicular to the crank measures 0.0015" greater than the nominal of all the other bores.
So my question is, if I size the forged pistons for the #2, #3, and #4 bores, will it still be within spec of the #1 bore?
I suppose worst case I could size them on the small side and have more piston slap. And then the fitment question would come down to ring gap. And in that case, if I file fit the rings, then there is no issue with #1 being bigger?
Assuming that the OOR and taper are not problems in themselves. They are within factory spec and I'm willing to go with them as-is. Worst case I have to scrap the block which is what I would need to do anyway. Then a new block would get bored to match the forged pistons. So there is no risk here in trying it.
Since its within spec for the factory and the rings would be the same anyway, then is it actually totally irrelevant that I'd be switching to forged, if they are sized for the same goal-bore as the stock cast pistons?