Motor build bearing/rings question M50

[Jon K]

The motor I am rebuilding has a good look to it nothing out of place or weird no odd wear or excessive wear. However, I am posed with the option of buying stock sized or over sized main bearings and piston rings. I intend to hone the block, but only to slightly x-hatch the walls, no boring or anything. Do people use standard or oversized rings? Also with the crank, do most people use stock size bearings or over size bearings? I can't see any notable "wear" on it - I am going to measure with a micrometer soon.

I know Dave M has done this - dave could use your insight and I forget the docs u may have sent me about rebuilding, have those?

[Dave M]

Stock sized rings if simply honing. Stock main and rod bearings. The block went 300k miles on these with no issues. I used Goetze rings as Winfred had made a derogatory remark about another manufacturer, the name of which I don't recall at the moment.

I also don't recall the documents I sent you. Could it be the torque specs for the lower end? Let me know what you need.

Dave

[Jon K]

Dave I feel humility in admitting that I need the bottom end torque specs again. I lost a RAID array last week.

[winfred]

stock sizes top and bottom, if theres a problem to where stock didn't fit id look for a better block or crank, deves rings were the royal pieces of ****, they suck

[632 Regal]

stock sizes unless the cylinders are bored and the crank was turned under which I believe is neither of your choices.

[The Bigfella]

The only way to determine what you need is to have it properly measured. I rebuilt a 45,000 km block in the M5 and used my 115,000 km crank in it. The crank only needed a linish and stock bearings. The block went from "0" to "00" rings after a hone. Then the ring gaps were measured and the end float was measured and the ........ everything, absolutely everything, was measured and compared to specs.

It is impossible to say what you need without measuring for ovality, etc.

[Ross]

If the crank looks good then try std. bearings, use plastigage to check clearance. I suspect you'll want to be on the wide side anyhow.
If you can't feel a ridge in the cylinders a light hone job and std. again.
Given your intentions for this motor I would not be too casual about clearances.

[Dave M]

Most everything is in here. Main and connecting rod torques are separated by a bunch of pages, go figure.

bmw torque value pdf. (http://www.hyrumswebsite.com/BMW_pdfs/bmw_torq.pdf)

[Jon K]

Dave do you have any specification for oil clearances on bearing/crank surfaces ata ll?