VG30 premature bearing failure help

Hey everyone, can I please ask people opinion on this premature main bearing failure.

The engine details are:

Nissan VG30DETT

Main Bearings King XP M4104STDX

Circumstances of the failure:

Fully forged engine build with all new components. Block line bored and honed as billet main caps with chromoly steel girdle fitted (in replacement of cast Nissan girdle)

It was “run in” on a SuperFlow 902 engine dyno (maybe 2hrs total run time). Then shipped to me in the U.K. and had a further 400-500 road mile break in period.

Car was then taken for dyno tuning.

During the dyno tune, a drop in oil pressure was noticed (from 106psi to 96psi at 7000rpm), so the dyno session was aborted for an investigation to take place. The engine was not run again.

The engine life is estimated to be around 500-600 miles of use.

All other temperatures were as expected (76c oil temp, 79c coolant temp), as evidenced in the datalog.

Oil filter removed and debris evident.

Oil sample taken and analysed, where no fuel dilution was found. High levels of silicon explained by all 4 cam covers being resealed with RTV on prior oil change.

Engine removed and disassembled, where cap side main bearing 2 and 3 were found to have suffered a failure. Main bearings 1 and 4 also had signs of wear, but had not failed.

No signs of heat transfer (blueing etc) evident on the backs of the bearings, caps, block or crankshaft. Crankshaft had smearing of copper on main journals 2 and 3.

Bearing clearing clearances listed on buildsheet by engine builder as 0.0033-0035”

Inspection of the crankshaft shows a 0.1mm deformation of both main journal 2 and 3

Inspection of the housing bores showed:

Housing journals DBG set to 2.6249” @20c temp

1 0.0024 tight to 0.001 tight, 0.001 taper front to back

2 0.0018 to 0.0014 tight

3 0.0014 tight 0.0007 loose 0.001 taper front to back

4 0.0015 tight 0.0004-6 taper front to back

This was significantly different to measurements provided on build sheet (Housing Bore listed as 2.6245” across all 4)

Measurement of the clearances on the two intact main bearings (1 and 4) across each bearing:

DBG 2.4805

*1

Pos. Front. Rear Tight/Loose

12-6 f. 0.0018 r 0.001 tight

2-8 .f 0.0028 r 0.0017 tight

3-9 f 0.0032 r 0.0024 tight

11-5 0.0024 r 0.0018 tight

DBG 2.4805

*4

12-6 f 0.0015 r 0.0019 tight

2-8 f 0.0015 r 0.00195 tight

3-9 f 0.0022 r 0.0026 tight

11-5 f 0.0016 r 0.0020 tight

Bearing thicknesses of 1 and 4 were measured

#1 Cap 0.0714, Block 0.0709

#4 Cap 0.0709, Block 0.0710

Thickness of block side bearing of 2 and 3 measured

#2 0.071

#3 0.0712

Measurements and inspections by two independent machine shops, showed the same measurements within 0.0002” across all inspected items.

Based on the above information, what would people’s opinion be as the cause of the failure.

King Bearings have been contacted in relation to this with the exact same information as above (awaiting reply).