So back to my original question, My crank measures within Standard wear tolerance with only (.0015 - .0018) difference 100k km or (60k miles) Use, no damage or marks on the journals, caps or bores , ACL have the STD X in .001 Undersized but my question is should i polish the journals for a more loose fit .0020-.0025 ? and have it even across all journals ? or just run with the standard size ACL X bearings.

Cheers

 

I'll venture addressing your question as far as I know based on personal experience. If your mains are standard size, get standard sized bearings and only a micro-polish on the crank. This has worked for me. Good luck.

 

When i built my engine (again) I had a rub in one of my crank bearing surfaces from when my oil pump failed. I ended up with the undersized bearings and the machinist kept the stock clearance, but towards the high. I was just in my engine (after only about 100 miles and a few dyno pulls) for more piston to wall clearance for higher boost other **** and it all looked good. I would think keeping everything as close to even across all bearings will help more so. I usually just ask my engine builder and go with what he says. Crank clearance is crank clearance, a good builder should be able to give you decent guidance there (oil pressure, oil weight, engine use). Generally from what I know alittle extra clearance helps in high HP motors.

 

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