Crankcase Main Bearing Bore Measurements

Main bearing bores in cylinder block assembly must be measured and resized (if necessary) whenever upper cylinder block and lower crankcase section are disassembled for repair.

1. Assemble lower crankcase section without crankshaft assembly or bearing inserts. Tighten all lower crankcase section mounting nuts by hand.
2. To align both upper and lower crankcase sections, install oil pump body and tighten 2 upper mounting bolts. Tighten lower crankcase mounting bolts to specification. Using an inside micrometer, cross-check main bearing bores and realign as needed.
3. Measure crankcase main bearing bores. Standard I.D. for all main bearing bores is 2.9528-2.9535" (75.000-75.019 mm). If bores are too small, ream to standard size. If bores are too large, ream (in 2 steps) to bearing oversize of 2.9626-2.9633" (75.250-75.269 mm).