Re: Balancing Flywheels for 345/392

[bearbvd@domain.elided (Greg Hermann)]

>So the bottom line is that if you need a new flywheel, as long as is the
>correct component for your engine, just bolt it on and forget about it.  You
>can't really do anything about it anyway.  You engine balance won't be so
>dramatically affected as to cause any problems.  But if your doing a rebuild,
>it's money well invested if you go ahead and have the engine balanced...
>especially if you start changing components like the pistons, connecting rods,
>harmonic balancer, flywheel, flexplate, etc.
>
John--

Thanks for an excellent explaination which I did not take the time to write!

However--my point remains--

Let's consider the 345 and 392.

Even though the stroke is the same, the pistons have very different weights
between the two engines because of the difference in bore size.

In a V-8, the weight of the pistons is an essential factor in arriving at
the mass of the "bob" weights at the two ends of the engine.

The difference in piston weights from a 345 to a 392 is more than enough
that, even at mass production balancing tolerances, the bob weight values
for a 345 and 392 would need to be substantially different.

This change could have been accomplished, on a production basis, either by
changing the bob weight values on the flywheel and the front damper, OR by
changing the mass (bob weight values) of the end counterweights on the
crank. One method or the other HAD to have been employed at the
factory--(surely not both). I do not know whether a 345 crank and a 392
crank are the same or different part #'s, do know that they are the same
stroke. Also do not know whether 345 and 392 flywheels and dampers are the
same part # or different--but I do know that one of the two had to change
between the two engines, even for mass production tolerances.

Same points as made above apply equally to 266 and 304 cranks, flywheels,
and front pulleys, as they also have the same stroke but different piston
weights.

Regards, Greg