<VV> Main Bearing Saga

[Bryan Blackwell]

This is from memory, hopefully someone will set me straight if I get it wrong.

When GM was developing the engine, there was some noise going on with some (not all) engines.  They never really worked out the cause and it didn't seem to hurt anything, but using a .001" offset on the number 4 main bearing made the noise go away so customers were happy.  For racing, at least some bearings were offered without the offset, as it wasn't really necessary in the first place.  I don't know if anyone ever did any specific testing in the later engines to see if the noise goes away with the longer stroke crank, I know GM kept the offset bearing through the production run.

For a performance application I'd run them.  For a street car, not sure.  If you did the worst thing would be an additional engine noise, but that might be enough reason.

--Bryan

> On Aug 9, 2022, at 7:29 AM, Juno Mail via VirtualVairs <virtualvairs at corvair.org> wrote:
> 
> I needed a set of standard size main bearings but our East Coast  (MASS) place was out of them.  Estimated time when they would have them was late November or early December!  I couldn't have the car out of action that long.  So, on a last chance I asked my friend who owns a NAPA store if he could get any.  Believe it or not, NAPA had 44 sets in a warehouse in Tennessee.  I ordered two sets.  They arrived yesterday. They are Sealed Power brand made in Mexico.  I was thrilled until I opened the box to find all three of the non-flanged bearing were the same.  No special Number 4 bearing.  I'm sitting here debating if I should use them.