<VV> (no subject)
corvairs at pacifier.com
Mon Oct 7 16:13:31 EDT 2013
Bob - I've never heard that story before. But stranger things have
happened in mass manufacturing.
Yet it raises more questions than it answers.
1) If "stealing" a no-flange bearing half from the run was acceptable
why not steal one of the usable full flange halfs?
2) How did the engineers know for certain that a half flange on #1 would
be adequate. Seems like a potentially huge design change (although, like
you said, years later we now know that it works fine)
And just for fun - how did Moraine make the mistake in the first place.
Flanged main bearings are honed as a pair. How would one half be wrong
but not the other (or maybe entire pairs were wrong and the factory had
to ...wait a minute that doesn't add up either.)
It would be interesting to know Moraine's production schedule and how it
matched with Tonawandas. It would seem that this "get by" move would
have only been used for a very short period of time yet a large
percentage of mains bearings (Moraines) pulled out of engines are half
Where does this story come from?
On 10/7/2013 12:29 PM, BobHelt at aol.com wrote:
> Hi Mark,
> Apparently you are not aware of the story, so here is a reasonable repeat
> of what happened.
> In About April 1962, the Tonawanda engine assembly plant discovered that
> their bearing supplier had supplied some #1 main bearings with "mis-matched
> flange" thicknesses. So production engineering studied the situation and
> found that those bearing couldn't be used as is, BUT production had to
> continue. So they issued a Tech Bulletin stating that only one half of the
> flanged bearing would be used and the other half would be the same as the #2 and
> #3 main bearings. Thus, production continued until the supplier could supply
> the correct #1 bearings.This correction happened toward the end of 1962.
> But unfortunately, this problem and the solution got announced to the
> bearing industry manufacturers and suppliers. So the bearing industry started
> manufacturing replacement bearings with this combination of half flanged #1.
> The whole industry converted. And they NEVER went back to the original
> configuration. But Chevrolet DID. So there are STILL many main #1s being made
> and sold with the half-flange.
> The good news is that the half-flange works perfectly well. It just looks
> Bob Helt
> I fully intend to check the clearances using
> full flanged bearings.
> Brian, that is all you can do. Maybe some blocks were machined differently
> for some reason and they did the half flange to prevent it from being too
> tight. Do check for that, my engine was at the inner limit with two flanged
> halves in there.
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