Crankshaft turning specs

[gnavs]

Hey guys,
after powering through 2.5 months of unemployment and funds being stretched to the max I think I'm finally ready to have the scratch machined out of my main bearing journal on my AAZ crank.  I know the undersized bearings are under by .25mm, .5mm and so forth but what is the overall diameter of the main that I should tell the machinist?  The scratch is barely noticeable but I can definitely feel it with my fingernail.  I'm sure one size under would be fine.
Any help is, as always, appreciated.  I hope to have this thing on the road by mid July.

[rallydiesel]

Keep in mind finding crank bearings past the 1st undersize is a major pita.

[gnavs]

very good to know, I'll do what I can to make sure this gets done right the first time.

[gnavs]

any help?

[Mark(The Miser)UK]

Any one explain, why a single circumferencial scratch needs to be machined out at all? I don't doubt that it looks 'horrid',
but I can see no freason why it needs removal, unless it is directly over the supply, and starves the rest of the bearing of oil.
Recent reading, of some old, but specialist books lead me to believe that a 'perfect' bearing is not the panacea, [er perfect goal (for you footy types)] and has it's disadvantages...

[gnavs]

I was having oil pressure issues before the teardown and I'm assuming it had some part to play in that.  It is a circumferential scratch indeed but I'd rather get things done right and try to avoid future issues.  Any more info is appreciated, this is my first rebuild and I'd like to avoid the "learning experiences"

[Mark(The Miser)UK]

Have you checked the oil pump for wear?
End play, at least, can be reduced with careful abrading on emery, of the housing.

[rodpaslow]

I would tend to agree, a circumferencial scratch is not such a bad thing, but without seeing the size I can't say for sure.  The early main shells #4 was a solid bottom like the other 4.  They changed it to be fully grooved due to oil problems.  The only bearings you can get for the last 10+ years have the grooved complete #4 main.  A scratch can hold oil, depending where and how big- sometime help, sometimes not.  Your decision..

[burn_your_money]

Giles can get first undersize bearings. We just bought some this week for a Golf he is fixing up. Topline makes them. They don't have the completely grooved #4 though.

[gnavs]

Tyler, I'll likely be contacted him for these bearings once I've got the crank finished up, I figure I may as well start fresh with no scratches as that's the way it would have come from factory (at least i would hope so).