I'm not sure if this is about new production ONLY or a repair:
Prior to 1948, the Chevy 235 (and 216) had an initial factory align-boring of the mains' saddle bores.
- The main bearing caps were then removed, and a brass layered shim pack was installed (these shims did not extend past the bearing parting-line) .
-- The main bearing semi-finished bearing shells were then installed (note: they were eccentric walled semi-finished bearing shells with thicker crowns than parting lines !!) The main bearing saddle bore at this stage was thus NO longer round in shape because of the additional shim pack. Main caps were then re-installed.
--- The main bearing semi-finished insert shells THEN needed to have an extra final align-reaming of the shells to get the inner diameter housing round (concentric) to mate with the crankshaft journals . This was because the main bearing insert shells were not a precision fit ... (the main bearing shells had a real thick babbitt linings that needed more honing/reaming to get proper final oil clearances).
---- SO, the early engines needed an 1) align-bore; 2) a cap removal and brass shims added;3) a cap re-install with rough insert main bearing shells...... 4) then a final stage of align-reaming of the insert shells to get the babbitt thinner, and the inner bearing shell housing round.
I may be using hone/ream switched around... but from what I understand you would bore to +.002/+.003 then hone (ream) to size. Seeing the production spec had only a +/- .0005 tolerance boring to size would be a difficult one shot endevour.
