rod bearing sizing on high-mileage motors

[Wayne]

David Pertuz wrote:
> Since I am one of those people who can elevate procrastination to 
> Olympic levels, 

I awarded myself the gold medal quite some time ago  ;)  I'd bet you 
wouldn't make bronze -- but that's good, really.

> I'll know what grade bearings it's got when I take the pans off, but 
> what should I put in there? Same grade(s), or one size bigger (tighter 
> clearance) on an engine with this mileage? For that matter, how can I 

I think you could get a mic' on there with the crank girdle removed, but 
  I can't say for sure.  The one time I did it in-car, I removed the 
girdle, but some say it can be accomplished without it.

The bearings are designed to take all the abuse they're soft alloy, the 
crank is hard.  I suspect there isn't that much crank wear.  Some of the 
bearing may smear or gall onto the crank, but unless the motor was about 
to grenade the crank should still clean up with ultra fine abrasive and 
have nearly zero wear.

Going on that assumption, I replaced with the identical size.  I also 
run the cars hard, and building in some extra bottom end oil clearance 
is recommended by many engine builders for extra endurance.  I think 
going a size tighter will end up too tight in most cases.

That's all just edumacated guessing on my part.  The bearing grades are 
less than 0.0002" steps anyway.  And I still think a little loose is better.

    -Wayne  '06 RSX-S / 93 SE-R / 93 NK2k / 90 Miata