<VV> #1 main bng

[lonwall@corvairunderground.com]

And that appears to be where it stands - clear as mud.  Oh well.

Thanks for the info Bob. Where is this from?


Lon Wall
www.corvairunderground.com


On 10/9/2013 7:14 AM, BobHelt at aol.com wrote:
> Hi Guys
> Here is another look at the #1 main bearing change after a little 
> research on the matter.
> Regards,
> Bob Helt
>
> It’s interesting to note that during the 1962 production run on 16 
> April 1962, there must have been a batch of incorrectly sized #1, 
> flanged main bearings received at the Tonawanda engine assembly plant 
> (Stated in a Tech Bulletin issued by Chevrolet). This mis-sizing 
> apparently was in the flange portion of the bearing, which controlled 
> the amount of endplay of the crankshaft. In order to use these 
> bearings without interruption to production, engine assembly continued 
> by using only a half-flanged #1 bearing. This was accomplished by 
> using just one of the pair of flanged inserts along with an insert 
> identical to the #2 and #3 bearings. Soon, after-market bearing 
> manufacturers were erroneously producing bearing sets with just the 
> half-flanged #1 main bearing.
>
> Now here is where the story gets interesting. The Tech Bulletin 
> definitely referred to a “mis match” of the two flange portions of the 
> #1 bearing. That would indicate a bearing supplier problem; and a 
> temporary problem until the supplier could resume supplying the 
> correct parts. Although we may never know just what happened to cause 
> to shift to the half-flanged bearing, we do know that for 1963 
> production new half-flanged bearing drawings were released. Why would 
> new drawings be released unless this was intended to be a permanent 
> change; or was there was another reason for the switch to half-flanged 
> bearings? Maybe this was done as a cost reduction instead, or even as 
> a solution to some other technical problem. Also for 1963 production, 
> the turbocharged engines received the new full-flanged aluminum 
> bearings. So for all of the 1963 production, except for the 150 hp 
> turbo engines, half-flanged bearings were used in production. One 
> would rightly assume that if it were a supplier problem, they would 
> have fixed the problem in much less time than a year and a quarter. So 
> it would look like the real reason for the half-flanged bearings was 
> something other than just a simple mis-matching condition.
>
> For the 1964 production, the factory converted entirely to the new 
> Moraine M400 Aluminum double-flanged bearings and continued to use 
> them until the end of production in 1969.
>
> Despite the fact that Chevrolet resumed production for 1964 using the 
> full-flanged bearing, the aftermarket bearing manufacturers continued 
> to produce these half-flanged bearings for all applications and all 
> years right up to the present day. Of course, the half-flanged bearing 
> will work satisfactorily, but most rebuilders prefer to use 
> full-flanged bearings as were used by the factory, except for this 
> short period during 1962-1963.
>
> In a message dated 10/8/2013 6:26:25 A.M. US Mountain Standard Time, 
> 62vair at gmail.com writes:
>
>     Lon, for #1, maybe they did both, steal a good flanged half and a
>     extra
>     un-flanged half to get two sets. Or,
>