<VV> #1 main bng

[Joel McGregor]

It's possible some bean counter decided it was better to just use the half flange so that the problem couldn't happen again and then for '64 the engineers won out.  Great historical info that helps us now.  Thanks!

Joel McGregor


________________________________________
From: virtualvairs-bounces at corvair.org [virtualvairs-bounces at corvair.org] on behalf of BobHelt at aol.com [BobHelt at aol.com]
Subject: Re: <VV> #1 main bng

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.