Hi Carlos,
You can't be absolutely sure what size the crank is without micing it.
The lack of marking "might" indicate that the shells are standard size, but
there is no absolute standard for bearing marking. It is never "safe to
assume" anything.
You could get an approximation by placing two bottom shells
together & measuring the ID. You could measure shell thickness to
compare but you don't have any other know shell sizes to compare to. It
is most likely that any shaft grinding was done in .010" increments.
In the end, there is no substitute for very precise measuring, which the
machine shop can do. Having the machine shop measure things is not a
"hassle", it is a necessity. The shop can give you a pretty good idea of
what size bearings to order. If they can't, look for another shop.You
really need to have the intended new bearings in hand before final crank
grinding, & they need to be installed in the block, measured, & compared
to the crank diameter. Crank size can be altered as needed. Bearing
shells cannot.
There are some short cuts & assumptions that could be made But a really
good shop will check everything twice. A .001" misfit can lead to disaster.
Good luck,
Dave Russell
Carlos Cruz wrote:
> Thanks to all that responded so far. I appreciate the input. The
> crankshaft is currently fitted with a Vanderbuilt Main Bearing. We
> have been unable to cross reference this bearing with anything that
> might offer some insight to what machining if any has been previously
> done by a PO.
>
> It's my understanding that the bearings are typically stamped with
> the size like .030 or .040. Knowing this up front might save me the
> hassle of having the maching shop mic it. In that knowning the
> bearing is already .040 tells me I'm looking at a crank that can't be
> salvaged and need a new one.
>
> Unfortunately this Vanderbuilt bearing has no such markings. Is it
> safe to assume that the bearing is of standard (STD) in size? Does
> anyone have experience with these Vanderbuilt bearings? I very much
> want to believe that the lack of markings does indicate STD and take
> some comfort that the machine shop can salvage the crank.
>
> Any help is greatly appreciated.
>
> Cheers, Carlos "Patiently waiting for the fun part to begin" Cruz
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