Re: Internal vs. External Balance

Date: Sun Feb 28 2010 - 16:34:18 EST

"Ray Block" <> wrote:
>> -----Original Message-----
>> From: Jamie Calder
>> I found a good article about balancing:
>> So if an externally balanced 360 needs a new harmonic balancer, flex plate
>> or flywheel (whichever the counter weight are attached to), does the new
>> part have to be taken to a machine shop so it can be balanced to match the
>> existing parts?
>> and which part does a 360 use to balance?

> Typically the 360 is externally balanced by the harmonic balancer AND the
> torque converter or flexplate. The factory put the rear weights on the
> converter. MP sells a kit of weights to install on the converter if you're
> building a 360 and only have a neutral converter to start with...i.e. one
> from a 318 or 340 or aftermarket.

> Other aftermarket companies (B&M, TCI, etc) have special flexplates for the
> 360 that eliminate the need to add weight to a converter. As long as the
> internals of the 360 are stock, the standard 360 balancer you can buy
> anywhere is the appropriate converter and/or weights or
> flexplate. No machine shop is needed in this instance.

     If I read what Ray (and others) are saying correctly, when
replacing a 360 harmonic balancer or torque converter or flexplate,
as far as the balance goes, the only differentiation is "318 vs 360"?
That is, there aren't a whole bunch of different ones built with
different balances so as to match the balance of your particular

    If that is the case, I am assuming that although the 360 is
"extermally balanced", the internal imbalance which requires this
external balance is exactly the same for every 360, there is no
variation from engine to engine?

    Assuming that I have understood correctly so far, rather than
imbalance each engine the same, why the heck didn't they just build
the 360 internally balanced in the first place? Seems like this would
save a lot of money since all harmonic balancers, flexplates and
torque converters could them be shared between the 318 and 360 with no
interchange worries or the resulting confusion? Were the 360 rods and
pistons simply too heavy to add enough weight to the crankshaft with
the block clearance involved? I'm assuming there must be some good
reason - given Chrysler's stinginess and overall solid engineering
reputation, it seems like there must have been some mitigating factor
here for this one to get by both the engineers and the bean counters.


Jon Steiger 
Steiger Performance

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