<VV> (no subject)

lonwall@corvairunderground.com 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?

Lon wall

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
> strange.
> Regards,
> 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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