rod bearing sizing on high-mileage motors

[Tim Rogers]

When I rebuilt my NX motor after the broken timing chain debacle, I ordered one grade tighter bearings than stock, then plastiguaged them all to make sure they gave the right clearance. It was just PM, they weren't knocking before and they're not knocking now.
Tim

---- David Pertuz <davidpertuz at mindspring.com> wrote:
> Since I am one of those people who can elevate procrastination to
> Olympic levels, I still have not replaced the rod bearings in my SE-R.
> They've been noisy (2500-3000rpm, mostly when cold) for a few k miles,
> but it helps that I didn't drive the car at all last year. But it is my
> preferred winter car since it's got the snow tires, and I want to do it
> soon when it's at least above freezing, before I take dying bearings too
> far and kill the crank.
>
> I've done this on the JDM engine that I put into my G20, so it's nothing
> new, but I am a little unsure about what grade bearings I should put in
> there. The G20's motor was low mileage, replacement done as due
> diligence, same grades put in, whereas this engine has 220k on it.
>
> 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
> practically measure the rod journals without dropping the crank down,
> which I do /not/ want to do since it will drastically increase the
> amount of work. Do I even need to measure the journals? I would think
> so. I want to do it right so I don't have to unbutton it again.
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